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Posted: 6/1/2009 10:54:15 PM EST
[Last Edit: 6/1/2009 10:55:14 PM EST by goodoleboy]


Just curious and contributing to the forum but how many Chinese M14 owners are shooting their guns with out a USGI bolt upgrade?

If you did do a bolt upgrade how many rounds did you put through it before upgrading? Was your upgrade needed at the time or done for other reason?

I am parent with 2 kids, wife, in school at 30 again, and having to only work part-time due my job cutting my hours.So funds are limited for upgrades, if I dont need them right away..
Not trying to start any arguments, believe me. I just want peace thats why I am up at 3 am posting while the kids are asleep not making any noise.
Link Posted: 6/2/2009 3:38:20 AM EST
I own two Polytech M14 rifles. One with lots of use, and one that I have fired some and rat-holed.

No new bolts needed yet. No sign of enlarging headspace. My favorite rifle is probably in the 4000 rounds fired range on the Chinese bolt.

Recoil springs would be my main concern. The Chinese springs are truely cheesey! A weak spring will allow the bolt to batter the back end of the receiver.
Link Posted: 6/2/2009 3:43:58 AM EST
[Last Edit: 6/2/2009 3:44:19 AM EST by H2O_MAN]
Replacing the op rod spring with a USGI or SpeedLock spring is an excellent idea and
having a new or like new USGI bolt stashed away for a rainy day is not a bad idea.
I also suggest picking up a Vortex M14 Flash Suppressor #2002V or M14 US Coast Guard / Navy Muzzle Brake #2001 from SEI
Link Posted: 6/2/2009 6:14:39 AM EST
Ive only got my one Polytech M14S IDE Side marked, only stuff Ive done is put a US stock on it. I have some parts waiting for me when I get home from deployment, No BS flash suppressor, op rod spring, and op rod locking pin. I bought a TRW marked bolt shortly after I bought it but havent needed to use it as my headspace is great. Mine was still in the box with only a few rounds down the pipe before I got it, but I'vee put at least 500 rounds down her myself.
Link Posted: 6/2/2009 9:01:19 AM EST
I bought mine used, so no clue how many actual rounds were on it, owner claimed ~500, put perhaps that many more through it ~1k total, before it started backing out/popping primers. Had the bolt done at that point.
Link Posted: 6/2/2009 11:17:15 AM EST
I put about 500 rounds through mine before I had the bolt upgraded. The rifle was functioning fine at the time. I just did the upgrade more for piece of mind.
Link Posted: 6/2/2009 12:32:56 PM EST
I got my Norinco from my father in law for christmas. He had bouht it new in the early 90's and shot it a lot. I bought gauge's and found the headspace long but in the "Safe if you don't want to save the brass realm". I actually swapped out that bolt with another brand new Chi com bolt. Bought from somebody who had done the USGI bolt swap. It now headspace's nice and tight per Nato spec's and I check it regularly and no "Growth" yet after about 200 rounds. For me checking headspace is part of my maintanace.
Link Posted: 6/2/2009 1:07:39 PM EST
Originally Posted By YoteSlayer69:
I got my Norinco from my father in law for christmas. He had bouht it new in the early 90's and shot it a lot. I bought gauge's and found the headspace long but in the "Safe if you don't want to save the brass realm". I actually swapped out that bolt with another brand new Chi com bolt. Bought from somebody who had done the USGI bolt swap. It now headspace's nice and tight per Nato spec's and I check it regularly and no "Growth" yet after about 200 rounds. For me checking headspace is part of my maintanace.


Are you checking it with a 7.62 NATO gauge? Sounds like that's what you are using and sounds like you know what you are doing with it.

A lot of the crap came from people using .308 gauges.

Link Posted: 6/3/2009 2:06:08 PM EST
I don't know how much help all be, but here is my experience so far.

Got a Chinese M14 a couple months ago. Advertised as a Polytech but I was told here it was a Norinco. Round count unknown and I refuse to shoot it until I check the headspace. It is mostly Chinese, as is the bolt, however I picked up a SA bolt just to be be on the safe side. I haven't decided whether to buy the gauges and check for myself or send off the rifle for the conversion and save my self the hassle of ordering gauges.
Link Posted: 6/3/2009 2:27:14 PM EST


I bought my Norinco M14 about 10 years ago from a guy who put about 500 or 600 rounds through it. I've only put about 600 rounds through it since I bought it so it's not been shot a lot but mine has been good to go with no problems in headspace.
Link Posted: 6/3/2009 2:44:03 PM EST
Originally Posted By Josh3239:
I don't know how much help all be, but here is my experience so far.

Got a Chinese M14 a couple months ago. Advertised as a Polytech but I was told here it was a Norinco. Round count unknown and I refuse to shoot it until I check the headspace. It is mostly Chinese, as is the bolt, however I picked up a SA bolt just to be be on the safe side. I haven't decided whether to buy the gauges and check for myself or send off the rifle for the conversion and save my self the hassle of ordering gauges.


Well, does it say Polytech or Norinco on it? How could someone here tell you what it was without seeing it?

Let's see, hundreds on a conversion that may not be needed versus about $60 or so dollars for gauges.

Hmmm, let me see, tough choice...............

Link Posted: 6/3/2009 5:36:46 PM EST
Originally Posted By LARRYG:
Originally Posted By YoteSlayer69:
I got my Norinco from my father in law for christmas. He had bouht it new in the early 90's and shot it a lot. I bought gauge's and found the headspace long but in the "Safe if you don't want to save the brass realm". I actually swapped out that bolt with another brand new Chi com bolt. Bought from somebody who had done the USGI bolt swap. It now headspace's nice and tight per Nato spec's and I check it regularly and no "Growth" yet after about 200 rounds. For me checking headspace is part of my maintanace.


Are you checking it with a 7.62 NATO gauge? Sounds like that's what you are using and sounds like you know what you are doing with it.

A lot of the crap came from people using .308 gauges.



Yes Nato gauge's Had em special ordered. I try to do as much research as possible this site has been a big help. Plus more than a few book's.
Link Posted: 6/3/2009 6:54:41 PM EST
Originally Posted By LARRYG:
Originally Posted By Josh3239:
I don't know how much help all be, but here is my experience so far.

Got a Chinese M14 a couple months ago. Advertised as a Polytech but I was told here it was a Norinco. Round count unknown and I refuse to shoot it until I check the headspace. It is mostly Chinese, as is the bolt, however I picked up a SA bolt just to be be on the safe side. I haven't decided whether to buy the gauges and check for myself or send off the rifle for the conversion and save my self the hassle of ordering gauges.


Well, does it say Polytech or Norinco on it? How could someone here tell you what it was without seeing it?

Let's see, hundreds on a conversion that may not be needed versus about $60 or so dollars for gauges.

Hmmm, let me see, tough choice...............



It probably says nothing other than a SN on the receiver and Century import marks on the barrel. If I recall correctly they also have a number under the wood like the Poly's and, I assume, the Norinco's.

Link Posted: 6/4/2009 10:39:47 AM EST
Originally Posted By Josh3239:
I don't know how much help all be, but here is my experience so far.

Got a Chinese M14 a couple months ago. Advertised as a Polytech but I was told here it was a Norinco. Round count unknown and I refuse to shoot it until I check the headspace. It is mostly Chinese, as is the bolt, however I picked up a SA bolt just to be be on the safe side. I haven't decided whether to buy the gauges and check for myself or send off the rifle for the conversion and save my self the hassle of ordering gauges.


Is there someone local who's competent with the M14? If so, take it to them and make sure you specify that 7.62 NATO gauges have to be used.

They probably won't charge you that much to check. Of course, gauges aren't a bad investment, so if you think you'll get use out of them, that might be the way to go.

Personally, I'd have it checked before doing anything.
Link Posted: 6/4/2009 1:35:48 PM EST
[Last Edit: 6/4/2009 1:37:30 PM EST by GeorgeCostanza]
What gauges are you guys using?

I got the .308 SAAMI (made by Forster) NO-GO Gauge and my heel stamped Poly M14S closes on this gauge no problem. My Poly also might close on a .308 SAAMI spec Field gauge, but even if it does, it really is not a problem since NATO Field gauge is .007" longer. I have never ever seen a NATO Field gauge before, so where do you get them?

Polytech's have "loose" chambers only when comparing it to SAAMI spec, but they are well within spec for 7.62 NATO. I don't really think a bolt conversion is needed, and I noticed the only people that say they are needed are the ones who make money from them, or guys who got it done for no reason other than so they can sleep better at night. As for myself, I'll pass on $600 bolt conversion.

7.62 NATO chambers are looser than .308 SAAMI, so only thing I see might be a problem is when using .308 Commercial ammo. Since commercial brass is thinner, your case "might" separate if you truly do have "loose" headspace.
Link Posted: 6/4/2009 1:42:44 PM EST
Originally Posted By GeorgeCostanza:
What gauges are you guys using?

I got the .308 SAAMI (made by Forster) NO-GO Gauge and my heel stamped Poly M14S closes on this gauge no problem. My Poly also might close on a .308 SAAMI spec Field gauge, but even if it does, it really is not a problem since NATO Field gauge is .007" longer. I have never ever seen a NATO Field gauge before, so where do you get them?

Polytech's have "loose" chambers only when comparing it to SAAMI spec, but they are well within spec for 7.62 NATO. I don't really think a bolt conversion is needed, and I noticed the only people that say they are needed are the ones who make money from them, or guys who got it done for no reason other than so they can sleep better at night. As for myself, I'll pass on $600 bolt conversion.

7.62 NATO chambers are looser than .308 SAAMI, so only thing I see might be a problem is when using .308 Commercial ammo. Since commercial brass is thinner, your case "might" separate if you truly do have "loose" headspace.


I have 7.62 NATO GO and NO GO gauges. Like you, I have never seen a Field gauge. Mine are by Clymer and I got them through CMP.
Link Posted: 6/4/2009 1:43:44 PM EST
Originally Posted By LARRYG:

I have 7.62 NATO GO and NO GO gauges.
Mine are by Clymer and I got them through CMP.


+1

Link Posted: 6/4/2009 2:02:43 PM EST
[Last Edit: 6/4/2009 7:41:33 PM EST by GeorgeCostanza]
Originally Posted By LARRYG:
I have 7.62 NATO GO and NO GO gauges. Like you, I have never seen a Field gauge. Mine are by Clymer and I got them through CMP.


How do you know it's NATO? I have seen Forster Gauges labeled "NATO" when they are not. Do you know the length of them?

Here is what Forster has as far as length goes for .308 SAAMI Gauges (as you can see these are .308 SAAMI specs)
1.630" –– Go
1.634" –– No Go
1.638" –– Field (Never Fire a .308 gun if HS measures this)

Since NATO specs allow for .007" longer, your "NATO" gauges should have the following measurements::
1.637 (or lower) –– Go
1.641 –– No Go
1.645 –– Field (I got this value from Fulton Armory's website, they say that Military M14's and M60's allow up to 1.6455 for headspace. I believe it too because when you resize milsurp brass such as LC you will see some of them way out of whack and really hard to resize due to being fired from guns with excessive headpace).

As you can see from above, the SAAMI Field Gauge is basically the NATO "GO" Gauge.

If anyone can show me a link of .308 gauges with the measurements it will be greatly appreciated. Basically I am looking for a 1.645 gauge, the gauge that tells me absolutely do not fire my gun if bolt can close with this in there.
Link Posted: 6/5/2009 1:57:15 PM EST
Originally Posted By GeorgeCostanza:
Originally Posted By LARRYG:
I have 7.62 NATO GO and NO GO gauges. Like you, I have never seen a Field gauge. Mine are by Clymer and I got them through CMP.


How do you know it's NATO? I have seen Forster Gauges labeled "NATO" when they are not. Do you know the length of them?

Here is what Forster has as far as length goes for .308 SAAMI Gauges (as you can see these are .308 SAAMI specs)
1.630" –– Go
1.634" –– No Go
1.638" –– Field (Never Fire a .308 gun if HS measures this)

Since NATO specs allow for .007" longer, your "NATO" gauges should have the following measurements::
1.637 (or lower) –– Go
1.641 –– No Go
1.645 –– Field (I got this value from Fulton Armory's website, they say that Military M14's and M60's allow up to 1.6455 for headspace. I believe it too because when you resize milsurp brass such as LC you will see some of them way out of whack and really hard to resize due to being fired from guns with excessive headpace).

As you can see from above, the SAAMI Field Gauge is basically the NATO "GO" Gauge.

If anyone can show me a link of .308 gauges with the measurements it will be greatly appreciated. Basically I am looking for a 1.645 gauge, the gauge that tells me absolutely do not fire my gun if bolt can close with this in there.


Call Clymer and tell em what you want and they will make em!...........thats what I did
Link Posted: 6/5/2009 2:49:21 PM EST
Originally Posted By GeorgeCostanza:
Originally Posted By LARRYG:
I have 7.62 NATO GO and NO GO gauges. Like you, I have never seen a Field gauge. Mine are by Clymer and I got them through CMP.


How do you know it's NATO? I have seen Forster Gauges labeled "NATO" when they are not. Do you know the length of them?



Mine are Clymer. They make .308 gauges as well. Silly me, taking their word for it.

Link Posted: 6/5/2009 2:58:13 PM EST
Originally Posted By LARRYG:
Originally Posted By GeorgeCostanza:
Originally Posted By LARRYG:
I have 7.62 NATO GO and NO GO gauges. Like you, I have never seen a Field gauge. Mine are by Clymer and I got them through CMP.


How do you know it's NATO? I have seen Forster Gauges labeled "NATO" when they are not. Do you know the length of them?



Mine are Clymer. They make .308 gauges as well. Silly me, taking their word for it.



Actually .308 and 7.62 NATO are the same. I am looking for the longer gauges. Just because it says 7.62 No-Go what does it really mean?

Do you have calipers? How long are your gauges is all I am asking... sheeeeesh! I remember some fool awhile back who insisted 7.62x51 NATO be called that and not .308. Are you him? I hate to break it to you but they are one and the same.
Link Posted: 6/5/2009 2:59:07 PM EST
Originally Posted By YoteSlayer69:

Call Clymer and tell em what you want and they will make em!...........thats what I did


Haha, great idea. I should have thought of that. I will give them a call to see what they got.
Link Posted: 6/5/2009 3:33:55 PM EST
[Last Edit: 6/5/2009 4:00:46 PM EST by LARRYG]
Originally Posted By GeorgeCostanza:
Originally Posted By LARRYG:
Originally Posted By GeorgeCostanza:
Originally Posted By LARRYG:
I have 7.62 NATO GO and NO GO gauges. Like you, I have never seen a Field gauge. Mine are by Clymer and I got them through CMP.


How do you know it's NATO? I have seen Forster Gauges labeled "NATO" when they are not. Do you know the length of them?



Mine are Clymer. They make .308 gauges as well. Silly me, taking their word for it.



Actually .308 and 7.62 NATO are the same. I am looking for the longer gauges. Just because it says 7.62 No-Go what does it really mean?

Do you have calipers? How long are your gauges is all I am asking... sheeeeesh! I remember some fool awhile back who insisted 7.62x51 NATO be called that and not .308. Are you him? I hate to break it to you but they are one and the same.


No, 7.62 NATO and .308 are not the same and the gauges are different if they are made properly. I just dug mine out, the numbers are too faded to see.

The fool is the one who insists they are the same. I guess that's why my Polytech and my Enfield 2A will fail a .308 gauge test but pass a 7.62 NATO gauge test, huh.

Your own post earlier in this thread belies that "they are the same" bit.

Read this:

http://www.303british.com/id36.html

While the dimension may be similar, there are many other differences such as case thickness. Also, when you are checking headspace, you are checking the chamber of the rifle and they sure as hell are not the same.
Link Posted: 6/5/2009 4:28:20 PM EST
[Last Edit: 6/5/2009 5:03:04 PM EST by GeorgeCostanza]
Originally Posted By LARRYG:

No, 7.62 NATO and .308 are not the same and the gauges are different if they are made properly. I just dug mine out, the numbers are too faded to see.

The fool is the one who insists they are the same. I guess that's why my Polytech and my Enfield 2A will fail a .308 gauge test but pass a 7.62 NATO gauge test, huh.

Your own post earlier in this thread belies that "they are the same" bit.

Read this:

http://www.303british.com/id36.html

While the dimension may be similar, there are many other differences such as case thickness. Also, when you are checking headspace, you are checking the chamber of the rifle and they sure as hell are not the same.


IT WAS YOU THEN!!! You are the dude who insisted 7.62x51 not be called .308 when 7.62x51 is truly .308!!! ahhaahah the legend himself, I met him!

That link you gave is old info my friend. Only thing different in 7.62 NATO and .308 SAAMI is that NATO chambers are "looser" meaning they have a wider tolerance.

But the ammo itself, .308 SAAMI and 7.62x51 NATO is one and the same. They have the same external dimension, the same pressure, and the same velocity. The only difference between the commerical stuff and military is the military uses thicker cases for it to allow for the looser headspace that a M60 or M14 might acquire in the field (to prevent case separation). But just because NATO uses thicker cases and has less volume, does not mean it is something else. It just means it will be loaded differently, about 10% less powder since the case is 10% smaller. You do know not all ammo is loaded the same right?

The confusion that .308 is 10k PSI higher is because the difference in measurement technique used. If you were to use the same measuring technique, there is only a 2k psi difference in pressure between regular Standard Commercial ammo and Military M80 ammo. But just because Military M80 is 2k under, does not turn it into a different round either, it just means it is under loaded. Military M118 is 52K PSI, the same as commerical .308 ammo.

If you shoot all kinds of ammo, you will see that 7.62x51 South African, 7.62x51 M80, Federal Gold Medal Match .308, and Federal American Eagle .308 ammo all almost have the exact same external dimensions, that .308 labeled ammo will vary with each other just as much as .308 varies with 7.62x51 labeled ammo.

Next thing you will tell me is that Wolf is not .223 because it is 2K under standard Commercial .223 Ammo.
Link Posted: 6/5/2009 4:35:36 PM EST
Norinco M14 owner here, I have not done any upgrade yet

eventually maybe, but it is still safe on gages, not showing any appreciable wear, so I am not going to worry for at least a little while
Link Posted: 6/5/2009 4:40:36 PM EST
Originally Posted By LARRYG:
I just dug mine out, the numbers are too faded to see.


I have never seen any that has numbers on them, the ones I have seen just say GO and NO-GO on them. You don't know how to use calipers?

Link Posted: 6/5/2009 4:54:27 PM EST
Originally Posted By GeorgeCostanza:
Originally Posted By LARRYG:
I just dug mine out, the numbers are too faded to see.


I have never seen any that has numbers on them, the ones I have seen just say GO and NO-GO on them. You don't know how to use calipers?



Have not been able to find my caliper since I moved into the house I bought in March.

And there are some numbers that are faded. I have seen gauges with numbers on them before.

Link Posted: 6/5/2009 5:00:36 PM EST
Originally Posted By GeorgeCostanza:
Originally Posted By LARRYG:

No, 7.62 NATO and .308 are not the same and the gauges are different if they are made properly. I just dug mine out, the numbers are too faded to see.

The fool is the one who insists they are the same. I guess that's why my Polytech and my Enfield 2A will fail a .308 gauge test but pass a 7.62 NATO gauge test, huh.

Your own post earlier in this thread belies that "they are the same" bit.

Read this:

http://www.303british.com/id36.html

While the dimension may be similar, there are many other differences such as case thickness. Also, when you are checking headspace, you are checking the chamber of the rifle and they sure as hell are not the same.


IT WAS YOU THEN!!! You are the dude who insisted 7.62x51 not be called .308 when 7.62x51 is truly .308!!! ahhaahah the legend himself, I met him!

That link you gave is old info my friend. Only thing different in 7.62 NATO and .308 SAAMI is that NATO chambers are "looser" meaning they have a wider tolerance.

But the ammo itself, .308 SAAMI and 7.62x51 NATO is one and the same. They have the same external dimension, the same pressure, and the same velocity. The only difference between the commerical stuff and military is the military uses thicker cases for it to allow for the looser headspace that a M60 or M14 might acquire in the field (to prevent case separation). But just because NATO uses thicker cases and has less volume, does not turn it into something else. It just means you it is loaded differently. You do know not all ammo is loaded the same right?

The confusion that .308 is 10k PSI higher is because the measurement technique used. If you were to use the same measuring technique, there is only a 2k psi difference in pressure between regular Standard Commercial ammo and Military M80 ammo. But just because Military M80 is 2k under, does not turn it into a different round either, it just means it is under loaded. Military M118 is 52K PSI, the same as commerical .308 ammo.

If you shoot all kinds of ammo, you will see that 7.62x51 South African, 7.62x51 M80, Federal Gold Medal Match .308, and Federal American Eagle .308 ammo all almost have the exact same external dimensions, that .308 labeled ammo will vary with each other just as much as .308 varies with 7.62x51 labeled ammo.

Next thing you will tell me is that Wolf is not .223 because it is 2K under standard Commercial .223 Ammo.


No, they are not the same. Did you even read the link? I am not even talking about PSI. Like I said, when you check headspace, you are checking the chamber and they are not the same. And the case thickness you dismiss is pretty vital as well. Yeah, I know it is loaded different and that does make it different ammo.

You can keep on believing they are the same, I don't care, but the truth is otherwise.
Link Posted: 6/5/2009 5:12:28 PM EST
[Last Edit: 6/5/2009 5:14:45 PM EST by GeorgeCostanza]
Originally Posted By LARRYG:
No, they are not the same. Did you even read the link? I am not even talking about PSI. Like I said, when you check headspace, you are checking the chamber and they are not the same. And the case thickness you dismiss is pretty vital as well. Yeah, I know it is loaded different and that does make it different ammo.

You can keep on believing they are the same, I don't care, but the truth is otherwise.


Yes I read a little and it is total BS based on info that is about 15 years old and WRONG..... and dude's like yourself pass it on as gospel so you have a whole new generation believing it.

NATO does not really have a minimum length for chambers, that a chamber that measures 1.630 is perfectly fine. But NATO does have a max of 1.6455, which is about .0075" longer than SAAMI Spec, the reason for this is it enables a gun to still fire properly when the chamber is really really dirty.

As I said above, NATO chambers are looser, but NATO ammo itself, be it SA, Port, or LC will have almost the exact same external dimensions as .308 commercial ammo, that variances between .308 SAAMI and 7.62 NATO will be the same as .308 with each other.

Feel free to thank me any time for the education lesson. Don't worry, I use to pass on the old info too, until I learned better. We all did it
Link Posted: 6/5/2009 5:16:53 PM EST
[Last Edit: 6/5/2009 5:25:59 PM EST by LARRYG]
Originally Posted By GeorgeCostanza:
Originally Posted By LARRYG:
No, they are not the same. Did you even read the link? I am not even talking about PSI. Like I said, when you check headspace, you are checking the chamber and they are not the same. And the case thickness you dismiss is pretty vital as well. Yeah, I know it is loaded different and that does make it different ammo.

You can keep on believing they are the same, I don't care, but the truth is otherwise.


Yes I read a little and it is total BS based on info that is about 15 years old and WRONG..... and dude's like yourself pass it on as gospel so you have a whole new generation believing it.

NATO does not really have a minimum length for chambers, that a chamber that measures 1.630 is perfectly fine. But NATO does have a max of 1.6455, which is about .0075" longer than SAAMI Spec, the reason for this is it enables a gun to still fire properly when the chamber is really really dirty.

As I said above, NATO chambers are looser, but NATO ammo itself, be it SA, Port, or LC will have almost the exact same external dimensions as .308 commercial ammo, that variances between .308 SAAMI and 7.62 NATO will be the same as .308 with each other.

Feel free to thank me any time for the education lesson. Don't worry, I use to pass on the old info too, until I learned better. We all did it


It's wrong because YOU say so? Not hardly.

Got a link to "correct" info?

You keep glossing over the fact that when you are checking headspace, you are checking the chamber, not the ammo.

Like I said, that "old" info that you say is wrong is why they put a warning in with the 2As to only shoot NATO ammo and why the 2A and the M14S will pass NATO gauges but not SAAMI gauges, huh.
Link Posted: 6/5/2009 5:31:44 PM EST
[Last Edit: 6/5/2009 5:55:38 PM EST by GeorgeCostanza]
Originally Posted By LARRYG:
It's wrong because YOU say so? Not hardly.

Got a link to "correct" info?

You keep glossing over the fact that when you are checking headspace, you are checking the chamber, not the ammo.


NATO chambers have a bigger tolerance.. key word here is TOLERANCE, but the ammo itself, .308 SAAMI and 7.62 NATO is the exact same. Go measure .308 labeled Federal Ammo with 7.62x51 ammo and you will see they are the same. AGAIN LET ME REPEAT, NATO CHAMBERS "MAY" HAVE A WIDER TOLERANCE, BUT THAT DOES NOT MEAN .308 AND 7.62X51 AMMO IS DIFFERENT.

The .308 vs. 7.62 NATO debate has been going on forever, even sites like Fulton Armory, and 6mm MBR list the wrong info. As a reloader I myself knew they were one and the same. They all measured the same, and pushed the bullet with the same velocities, so what made them different? Because they are not different!

The only problem with shooting Commerical ammo in 7.62x51 chambers only exist for some guns, such as the Ishapore. The Ish chambers measure even longer than the 1.6455 NATO Field Gauge! But despite this, it is still safe to shoot NATO labeled ammo through them because NATO cases are thicker. Commercial ammo through these guns and the case will separate. It is because of the out of spec chambers of this gun is why the World thinks there is a difference between 7.62 NATO and .308.

I found a lot of good info on the FALfiles that backed up what I believed all along. There is recent info posted on this. I will try to look for it just for you. In the meantime check out this pic, can you tell which one is .308 and 7.62x51? No you cannot because there is no difference, they are the same!

Link Posted: 6/5/2009 5:40:25 PM EST
[Last Edit: 6/5/2009 5:48:38 PM EST by GeorgeCostanza]
I found it on FALfiles. You must register on the FALfiles to view postings so I'll post the info here again.

Like I said, don't feel bad for passing on the wrong info, we all did it because we did not really know better. We trusted the "experts" like Fulton Armory and 6mmMBR.com because we just thatought they knew, but the truth is they really do not know. It is not until you shoot, measure, and chrono all types of ammo when you notice there is not any difference between them at all.

Feel free to thank me anytime. A simple "Thank you George" is good enough for me



Some fairly current information on this.
Copyright © 2008, Cross Connect Corp. All rights reserved Page 1
The Truth About 7.62x51mm NATO and 308 Winchester
By FALPhil


Introduction

The internet firearms and shooting culture is a relatively close knit group and very computer savvy, as hobby groups go. Many of the community are members of the several dozen discussion groups that revolve around the special interests of gun owners. Because of the nature of the internet and the inherent tendency of human beings towards believing anything that sounds reasonable, without applying critical thinking skills (probably a result of trends in government school systems – but that is another treatise), there is much misinformation available to the casual gun enthusiast about a variety of subjects concerning firearms.

One of the most pernicious of these “urban legends” is that there is a significant difference in the pressures between the 7.62x51mm NATO cartridge and the 308 Winchester cartridge. The misinformation indicates that using the commercial offering in a military weapon will visit death and destruction of biblical proportions upon the miscreant who would attempt such a thing.

I first ran into this ugly rumor in 1996, while participating on the rec.guns usenet forum. It made for interesting reading. At one point, a well-known Highpower Match competitor, who will remain unnamed, asked the question, “Why would you expect significant differences in pressure when commercial and
military cartridges are loaded with the same technology (powders, primers, cases, and projectiles) and the velocities are very close to each other?” This issue reared its ugly head a couple of years ago when the many boatloads of Ishapore 2A1 rifles hit the US shores. Much disinformation about what was safe in these fine rifles was bandied about over the internet.

That got me to thinking. My brother had been a lab technician at Aberdeen Proving Grounds in the late ‘70s, so I called him to ask him about it. It turns out that he worked on artillery dispersal, but he still knew some technicians involved in small arms research. He said he would reach out to them and get back to
me with some information.

About a month later, my brother called and described to me the method (in general terms) by which small arms ammunition is tested by the US Army. After speaking to him, I came to my own conclusion that 308 Winchester and 7.62 NATO were completely interchangeable. However, I am an unknown to many firearms enthusiasts. So, in order to support my position, I have performed a little research and documented my findings.


The Cartridges

The .308 Winchester is a rifle round and is the commercial version of the military 7.62x51mm NATO centerfire cartridge. The .308 Winchester was introduced in 1952, two years prior to the NATO adoption of the 7.62x51mm NATO or T65 round as it was known during testing. Winchester (a subsidiary of Olin Corporation) branded the cartridge and introduced it to the commercial hunting market as the 308 Winchester. Winchester's Model 70 and Model 88 rifles were subsequently chambered for the new cartridge. Since then, the .308 Winchester has become one of the most popular short-action big-game hunting cartridges in the world. It is also commonly used for civilian target shooting, military sniping, and police sharpshooting.

The purpose of the T65 was to achieve the same or similar performance of the then-standard 30-06 cartridge in a package that was more conducive to reliability in fully automatic weapons and infantry weapons under extreme conditions. A weight savings was a by-product of the project, but it was not a
primary consideration.

While Winchester intended the T65 (later named 7.62x51mm NATO) and 308 Winchester ammunition to be identical and fully interchangeable, there are some differences. The two primary differences are the specification of chambers size between the two, and the construction or the cartridge case.


Chamber Size

Look at the table below. The right column represents a military headspace gauge specification; the left one, the SAAMI specification. With many military rifles, the chambers can be significantly longer than say, a Remington 700. Note that the military chamber would fail a NO GO check with a SAAMI gauge, but
pass a FIELD check using the proper military gauges.

There is a .013" difference in acceptability, between these two specifications. This is significant in that, for reloading purposes, brass will stretch more in a military chamber upon firing, thereby reducing the life of the brass and possibly promoting case head separation. But that additional length will allow a round to chamber in an incredibly dirty weapon, which is a requirement for military applications.

308 Winchester (SAAMI) Headspace 7.62 NATO (Military) Headspace
GO - 1.6300" GO - 1.6350"
NOGO - 1.6340" NOGO - 1.6405"
FIELD - 1.6380" FIELD - 1.6455"

However, it must be noted that this is the chamber specification and not the ammunition specification. The external dimensions of the two types of ammunition are nearly identical Cartridge Case Construction.

In my personal experiments, I have found, on average, that commercial 308 Winchester cases are able to contain approximately 58 grains of water, on average. The average for Lake City 92 cases, according to my measurements approached very close to 56.2 grains of water, and for Portuguese NATO markedcases which are Berdan primed, the average was close to 55.9. All brass had been fired once was sized with the same die, a Hornady New Dimension 308 Winchester die.

These water measurements indicate that, for the military cases, the brass is thicker. This finding was not unanticipated, as the military brass weighs more, and the military specification calls for the “beefing up” of the area around the web for the purpose of providing an additional safety margin in case the cartridge is fired in an automatic weapon and the charge is ignited before the cartridge is completely in battery in said weapon.

This characteristic also has implications for hand loaders and other enthusiasts where pressure is concerned. More on that later



Regulating Bodies

The American Sporting Arms and Ammunition Manufacturers' Institute (commonly abbreviated as SAAMI and pronounced "Sammy") is an association of American firearms and ammunition manufacturers.

SAAMI publishes various industry standards related to the field, including fire code, ammunition and chamber specifications, and acceptable chamber pressure. SAAMI is an example of industry selfregulations.

In the United States firearms and ammunition specifications are not overseen by the Consumer Product Safety Commission or any other branch of government. Firearms enthusiasts should be aware that only manufacturers that are members of SAAMI are bound by the Institute's guidelines. All other adherence to SAAMI specifications is strictly voluntary.

The European equivalent of SAAMI is the Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives (Permanent International Commission for Testing Portable Firearms, commonly abbreviated as C.I.P. or CIP). CIP is funded and mandated by several governments that are part of the
European Union.

There are two other organizations that are germane to this discussion. They are the US Army and the North Atlantic Treaty Organization (NATO). Each has its own specifications and testing methodologies which are not influenced by commercial interests unless there is a very good reason.


Pressure

Despite working together, the two main industry standards organizations SAAMI and C.I.P. have assigned different standards for some cartridges. This leads to officially sanctioned conflicting differences between European and American ammunition and chamber dimensions and maximum allowed chamber
pressures.

Under SAAMI proof test procedures, for bottlenecked cases the center of the transducer is located .175" behind the shoulder of the case for large diameter (.250") transducers and .150" for small diameter (.194") transducers. For straight cases the center of the transducer is located one-half of the transducer
diameter plus .005" behind the base of the seated bullet. Small transducers are used when the case diameter at the point of measurement is less than .35".

Under C.I.P. proof test standards a drilled case is used and the piezo measuring device (transducer) will be positioned at a distance of 25 mm from the breech face when the length of the cartridge case permits that, including limits. When the length of the cartridge case is to short, pressure measurement will take place at a cartridge specific defined shorter distance from the breech face depending on the dimensions of the case. The difference in the location of the pressure measurement gives different results than the C.I.P. standard.

According to the official C.I.P guidelines the .308 Winchester (referred to as 7.62x51 by CIP) case can handle up to 415 MPa (60,190 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.

The .308 Winchester and 7.62x51mm NATO cartridges are not identical and there are minor differences in their inner case dimensions, though SAAMI does not list either cartridge as unsafe in a firearm designed for use with the other. [http://www.saami.org/Unsafe_Combinations.cfm].

NATO EPVAT testing is one of the three recognized classes of procedures used in the world to control the safety and quality of firearms ammunition. EPVAT Testing is described in unclassified documents by NATO, more precisely by the AC/225 Army Armaments Group (NAAG). EPVAT is an abbreviation for "Electronic Pressure Velocity and Action Time". This is a comprehensive procedure for testing ammunition using state-of-the-art instruments and computers. The procedure itself is described in NATO document AC/225 (Com. III/SC.1)D/200.

Unlike the C.I.P. procedures aiming only at the user's safety, the NATO procedures for ammunition testing also includes comprehensive functional quality testing in relation with the intended use. That is, not only the soldier's safety is looked at, but also his capacity to incapacitate the enemy. As a result, for every ammunition order by NATO, a complete acceptance approval on both safety and functionality is performed by both NATO and the relevant ammunition manufacturers in a contradictory fashion. For this, a highly accurate and indisputable protocol has been defined by NATO experts using a system
of reference cartridges.

The civilian organizations C.I.P. and SAAMI use less comprehensive test procedures than NATO, but NATO test centers have the advantage that only a few chamberings are in military use. The C.I.P. and SAAMI proof houses must be capable of testing hundreds of different chamberings requiring lots of different test barrels, etc..[7.62 mm. STANAG 2310 and NATO Manual of Proof and Inspection AC/225 (LG/3-SG/1) D/9.]

The US Army continues to use (as of 1995) the M-11 Copper Crusher device for pressure measurements of small arms ammunition. The M-11 was enhanced, when in 1982, it was noted that the results generated at the high end of the test range did not meet NATO standards. [Defense Technical Information Center, ARMY BALLISTIC RESEARCH LAB/APD, Accession Number : ADP000024]

What is interesting to note is that around the time of the engineering change to the M-11 Copper Crusher device, the US Army changed the units of measurement for the device from PSI to Copper Units of Pressure, or CUP. Both SAAMI and CIP used the copper crusher method until the advent of inexpensive, reliable piezoelectric strain gauges, at which point, both organizations converted their methodologies to
take advantage of the newer technology.

The copper crusher method was the standard for small arms pressure measurements since the late 1800s. A copper pellet just like a small watch battery in placed in the test pressure chamber which is attached to the cartridge chamber, the test round is fired and the copper pellet is then measured with a micrometer. The micrometer measurement is then converted into a PSI reading by using a chart that converts the length of the pellet into a pressure reading. The charts are constructed using the theoretical modulus of compression for the particular copper alloy used in the pellet, and may or may not have any relation to the actual absolute pressure. BUT, the results of the copper crusher method are always relative to previous results, which allows for determining what is safe and what is not.

Both SAAMI and the CIP have detailed specifications for the arrangement and dimensions of the copper crusher. Because these two systems are not identical, the two crusher standards cannot always agree. Further, as explained above, CIP crusher ratings are generally a bit higher than SAAMI's due to differences in definitions. Also, SAAMI is generally more conservative with older military rounds, such as the 8mm Mauser.

With the SAAMI methodology, the piston is positioned over the brass case, and the case will rupture somewhere below 20,000 PSI. The resulting sudden jump in pressure under the piston magnifies problems with piston inertia, and this makes the reading more sensitive to parameters such as burning rate, case strength, and true peak pressure. The CIP methodology requires the piston case be drilled at the sensor location, and the benefit is that crusher and piezoelectric ratios are much more consistent from cartridge to cartridge, allowing them to reasonably use a conversion formula.



Pressure Confusion

However, neither method addresses the figure “50,000 PSI” that is so often misquoted, especially by “expert” sources such as 6mmbr.com and surplusrifle.com.

This figure comes from the US Army in various technical manuals, most notably, TM-D001-27
Copyright © 2008, Cross Connect Corp. All rights reserved Page 6. The real problem is the confusion between the old and the new methods of pressure testing. The old pressure testing method used for the 7.62 NATO cartridge started out life in the 1950s and is still published today in the US Army Technical Manuals. The figures are based on the copper crusher method in CUP, but are published as PSI.

The new method is the piezoelectric strain gauge transducer method; it is the same technology used today to show an automobile’s oil pressure. The piezoelectric strain gauge transducer pressure method is a direct pressure reading based on an absolute standard, where the older copper crusher method a conversion based on a relative measure and a conversion chart. And this is why you see the difference in the pressure readings, but the older 52,000 CUP is equal to 62,000 PSI (piezoelectric transducer method).

Today, these two methods are called CUP and PSI and the readings are different, but 52,000 CUP equals 62,000 PSI and both are the same pressure, similar to the way 60 MPH equals 100 KPH.

To add even more confusion about the Ishapore 2A1, which started me on this article, many shooters want to use the headspace specifications set by NATO, which is different from what the Indian Army set for the Ishapore rifles.

In the figure below, you can actually see a page from an older reloading manual in which equivalent loads are portrayed in both CUP (C) and piezoelectric transducer PSI (P). Copyright © 2008, Cross Connect Corp. All rights reserved Page 7

Karl Kleimenhagen points out:
In Denton Bramwell's article [http://www.shootingsoftware.com/ftp/psicuparticle2.pdf], a formula is derived using a basic statistical analysis of SAAMI's ratings, covering only pressures between 28,000 and 54,000 CUP : piezo = 1.52 * crusher - 18

He also demonstrates that within this pressure range, the CIP appears to have generally used a simple conversion between their crusher and piezo ratings, roughly equal to: piezo = 1.21 * crusher - 2.8
CIP pressures are multiples of 50 bar (about 700 psi), probably rounded after the conversion. (Please note that CIP crusher readings should not be equated with SAAMI CUP crusher readings.)

In the 09/1968 issue of Handloader, Lloyd Brownell presents test data (crusher, but not necessarily CUP) which suggests a linear conversion formula is not the best choice, and in my Powley Computer I use:
piezo = crusher * ( 1 + ( crusher^2.2 )/30000 ) From 0 to about 60 ksi crusher, it fits both SAAMI's ratings and Brownell's data well, but it is low at the high end of Brownell's data. Brownell's data shows little to no error below 20 ksi, and a curve fit to only his data between 20 and 67 ksi crusher is: piezo = crusher + ( (crusher - 20) ^ 2.3 ) / 210

Conclusions
The pressure difference between the two rounds is insignificant, the real problem is commercial ammunition has thinner cases that were not designed to shoot in military chambers BUT we do it all the time anyway and this why you see more case head separations on commercial cases fired in military chambers.

The M118 special long range round is loaded to 52,000 CUP (all other U.S. 7.62mm are 50,000 CUP) which would be equal to the pressure levels of commercial ammunition, this means actually there is no pressure difference between the .308 and 7.62 NATO for the M118 cartridge.

No accurate conversion between copper crusher and true pressure exists, but approximations can be made. In all the conversions outlined above, pressures are in thousands of PSI (KPSI). Expect errors of several KPSI, or about 15%, with such formulas. Many factors determine how much the indicated pressure reading from a crusher misses the true pressure, and the error varies among cartridges and even among different loads for one cartridge. The conversions might be accurate enough for many practical purposes.

So, to sum everything up, the pressure difference between the 308 Winchester and the 7.62x51mm NATO is less than 2,000 PSI which is statistically insignificant. The same pressure variation may be achieved by firing any rifle on a hot day and on a cold day or by changing brands of primers. It is safe to shoot 308 Winchester in your 7.62x51 rifles (even the Ishapores) and vice versa. Handloaders should be aware that they should reduce the amount of powder when using military 7.62 NATO cases by about 10- 12% and work up to safe pressures with corresponding velocities.

References:
[1] ANSI/SAAMI document Z299.4-1992 is the principle source for the SAAMI crusher and piezoelectric
ratings listed here. The ratings listed are the "maximum average pressure". The book they offer is dated
and doesn't include the ratings of newer commercial cartridges. The procedures and definitions should be
current.
[2] The CIP documents are available on their site, and these were the reference for CIP procedures,
definitions, and piezoelectric ratings. In these, past standards for crusher ratings are no longer listed.
Instead, they refer you to past editions when proofing for a cartridge for which no current standard exists.
[3] The Soapbox of Karl W. Kleimenhagen (http://kwk.us/)
[4] Accurate Reloading Guide -
http://www.accuratepowder.com/data/...le/Standarddata(Rifle)/308Cal(7.82mm)/308%
20Winchester%20Pages%20260%20to%20262.pdf
Link Posted: 6/5/2009 6:01:20 PM EST
[Last Edit: 6/5/2009 6:02:32 PM EST by LARRYG]
Tell you what, you keep going in circles and repeating yourself, convinced that you are superior.

One more time, you can spout all you want about the ammo, but when you check headspace, you are checking the chamber. That doesn't seem to get through to you nor does the fact that some rifles have warnings to shoot only NATO ammo. I guess they are wrong as well.

And nothing makes that any more accurate than what I linked to. It just happens to fit your agenda.

Who is to say that they are correct?

So, have fun with yourself. You are wrong, End of story.
Link Posted: 6/5/2009 6:13:27 PM EST
[Last Edit: 6/5/2009 8:41:28 PM EST by GeorgeCostanza]
Originally Posted By LARRYG:
Tell you what, you keep going in circles and repeating yourself, convinced that you are superior.

One more time, you can spout all you want about the ammo, but when you check headspace, you are checking the chamber.

And nothing makes that any more accurate than what I linked to. It just happens to fit your agenda.

Who is to say that they are correct?

So, have fun with yourself. You are wrong, End of story.



It's ok to be stubborn too. We don't mind you being stubborn. Go ahead and keep on passing the wrong info, I am sure you will have your fanboys that follow you no matter what I say. I know I can lead a horse to water but I can't make him drink it

When you are checking headspace you are checking the length of the chamber of what can be safely fired through the gun. NATO spec allows the chamber to be up to 1.6455", but not all NATO chambers are this long. Some Military M60, Some Military M14's, and Polytech M14S has chambers this long, but it does not mean all NATO marked chambers are this long. I just happen to know my M14S can safely fire a .308 SAAMI or 7.62 NATO round if it's headspace is less than 1.643 (I want a gauge .002 lower than the NATO max, but .005 above the SAAMI max

Here I will repeat: The only problem with shooting Commerical ammo in 7.62x51 chambers only exist for some guns, such as the Ishapore. The Ish chambers measure even longer than the 1.6455 NATO Field Gauge! But despite this, it is still safe to shoot NATO labeled ammo through them because NATO cases are thicker. Shoot Commercial ammo through these guns and the case will separate. It is because of the out of spec chambers of this gun is why the World, thanks to your help, thinks there is a difference between 7.62 NATO and .308.


Key is to know what the length of what the Gauges are. "GO", "NO-GO" and "Field Reject" really mean nothing as we already proved that a "Field" gauge for one gun can mean a "GO" gauge for another gun.
Link Posted: 6/5/2009 7:48:04 PM EST
Just to remain off topic:
George can you describe the method that you use to measure your HS gauges? I'm finding it difficult to accurately locate the calipers to the 0.400" datum line in the shoulder (not marked on any gauge I've seen) where the headspace measurement is taken.
Link Posted: 6/5/2009 8:15:56 PM EST
[Last Edit: 6/5/2009 8:33:47 PM EST by GeorgeCostanza]
Originally Posted By 1811GNR:
Just to remain off topic:
George can you describe the method that you use to measure your HS gauges? I'm finding it difficult to accurately locate the calipers to the 0.400" datum line in the shoulder (not marked on any gauge I've seen) where the headspace measurement is taken.


I only have the Forster NO-GO gauge and Forster list their NO-GO gauge as 1.634" so I already know how long it is. Basically I have no idea where the datum line is since it is not marked on the gauge. I am not in front of my gauge right now to take a measurement, so I'll have to get back with you on how the rest of this NO-GO gauge measures.

According to Brownell's, Forster sells a 1.630" to 1.638" gauges in .001" increments. Notice how all the Forster gauges are labeled "NATO" regardless of what length they are, so unless you know the length, the term "NATO" does not really mean jack. Technically they are all NATO gauges Brownells Forster .308 gauges

Me thinks for a real USGI M14 and Polytech, the most useful gauge will be a 1.6455 or maybe even a 1.644" (just to be a little safer). I will call Clymer on Monday to see what they have.

Link Posted: 6/5/2009 8:23:48 PM EST
I use my Norinco mainly for Elk hunting and only had the headspace checked once by a gunsmith school. I don't shoot a lot of rounds, maybe 500 total and it still shoots well so I am not going to worry.

Link Posted: 6/5/2009 8:33:43 PM EST
lol,have to love this thread...who has i chicom,that still hasent blown up on you yet?

sound off
Link Posted: 6/5/2009 8:52:09 PM EST
I have a Norinco that the previous owner claimed to have fired over a thousand rounds through. I had the headspacing checked after I purchased it and was told it was within spec for 7.62X51NATO but, a little loose for .308 WIN. Since then I have fired close to three hundred rounds of Federal PSP and Winchester M80. I plan on leaving the original bolt in place until it has problems AKA split brass, protruding/proud primers. Personally it doesn't worry me at all and it will not stop me from enjoying what I consider to be a really nice rifle. I have upgraded to a USGI stock, flash suppressor and plan on a few more changes in the future but, changing the bolt just for the sake of changing the bolt seems to me pretty silly...YMMV
Link Posted: 6/5/2009 9:05:59 PM EST
Originally Posted By shadrach:
I have a Norinco that the previous owner claimed to have fired over a thousand rounds through. I had the headspacing checked after I purchased it and was told it was within spec for 7.62X51NATO but, a little loose for .308 WIN. Since then I have fired close to three hundred rounds of Federal PSP and Winchester M80. I plan on leaving the original bolt in place until it has problems AKA split brass, protruding/proud primers. Personally it doesn't worry me at all and it will not stop me from enjoying what I consider to be a really nice rifle. I have upgraded to a USGI stock, flash suppressor and plan on a few more changes in the future but, changing the bolt just for the sake of changing the bolt seems to me pretty silly...YMMV


what is the life expectansy on a springer or any other american made bolt/rifle?
Link Posted: 6/5/2009 11:01:39 PM EST
1 Norinco & 2 Polytechs later and all are still shooting fine....
Link Posted: 6/6/2009 2:14:30 AM EST
My Norinco was very close to closing on the Field gauge. It went 2/3 down anyhow. Yeah it suppose to still be safe.. I know that. I then put layout fluid ( ink ) on the lugs. Guess what... I had probably 40% lug contact.... That's not good enough for me and my eyes and face...... WarDawg
Link Posted: 6/6/2009 9:43:15 AM EST
This is info from Forster for their 7.62 NATO gauges:
7.62 NATO (Minimum chamber) – length is 1.6355” plus .0003” minus zero P/N HG762NATOMin

7.62 NATO (Maximum chamber) – length is 1.6455” plus Zero minus .0003” P/N HG762NATOMax

After further research it seems that the 1.6455" gauge is only used with a test bolt to determine if the receiver is unserviceable. The Field length gauge is 1.6415" for the M-14, the book The FAL Rifle by Blake Stevens lists max headspace for the FAL as 1.6405".

GC, I was kinda being a smarta**, good luck measuring to the datum line with a caliper

On topic:
Haven't shot my Poly enough to say how long the factory bolt will hold up. Dang near closes on the 1.6455" Forster gauge...
Link Posted: 6/6/2009 10:13:07 AM EST
[Last Edit: 6/6/2009 10:59:29 AM EST by GeorgeCostanza]
Originally Posted By 1811GNR:
This is info from Forster for their 7.62 NATO gauges:
7.62 NATO (Minimum chamber) – length is 1.6355” plus .0003” minus zero P/N HG762NATOMin

7.62 NATO (Maximum chamber) – length is 1.6455” plus Zero minus .0003” P/N HG762NATOMax

After further research it seems that the 1.6455" gauge is only used with a test bolt to determine if the receiver is unserviceable. The Field length gauge is 1.6415" for the M-14, the book The FAL Rifle by Blake Stevens lists max headspace for the FAL as 1.6405".

GC, I was kinda being a smarta**, good luck measuring to the datum line with a caliper

On topic:
Haven't shot my Poly enough to say how long the factory bolt will hold up. Dang near closes on the 1.6455" Forster gauge...


Awesome! Thanks for the info. The 1.6415 is the one I want, that is basically the NO-GO gauge for the Polytech.
Link Posted: 6/6/2009 10:38:03 AM EST
OK, I found my Dept of the Army Tech Manual, TM 9-1005-223-34.

Four sizes of HS gauges are listed:
1.6355"
1.6375"
1.6415"
1.6455"
Basically, if the bolt closes on the 1.6455" then check it with the test bolt. Doesn't close on test bolt, replace bolt. Closes on test bolt = unserviceable receiver.
Link Posted: 6/6/2009 6:23:26 PM EST
You know no one here has mentioned how to check your exact headspace. Anybody?........Hint........Think of headspace gauge's like feeler gauge's
Link Posted: 6/6/2009 6:49:47 PM EST
Originally Posted By YoteSlayer69:
You know no one here has mentioned how to check your exact headspace. Anybody?........Hint........Think of headspace gauge's like feeler gauge's


yeah, don't slam those suckers in as if you are chambering a round or you will ream your chambers

gentle tap, very gentle is the key.
Link Posted: 6/7/2009 10:02:59 AM EST

Originally Posted By H2O_MAN:
Replacing the op rod spring with a USGI or SpeedLock spring is an excellent idea and
having a new or like new USGI bolt stashed away for a rainy day is not a bad idea.
I also suggest picking up a Vortex M14 Flash Suppressor #2002V or M14 US Coast Guard / Navy Muzzle Brake #2001 from SEI

FROM SEI... NO WAY!
Link Posted: 6/13/2009 7:27:58 AM EST
Link Posted: 6/13/2009 7:33:31 AM EST
[Last Edit: 6/13/2009 9:44:57 AM EST by LARRYG]
Originally Posted By booger-hooker:
Polytech I have only has a few hundred rounds thru it and no problems what so ever. This M1A M14S was gone thru by Ron Smith in Phoenix and had it all checked out...bolt was fine and the hardness was all found to be at or above level of a Springfield. I have no problems shooting this rifle (although it's been about 4 years since the last time) but would like to get a spare USGI bolt and springs sometime just to have around.




Link Posted: 6/13/2009 12:04:51 PM EST
I am a NorincoM14S owner. I have a TRW bolt which my children will inherit if that tells you anything. The bolt scare is a good way to sell an expensive and usually unnecessary service. Fulton's kids have to eat too.
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