Quoted:
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.

Quoted:
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.

Quoted:


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.

Quoted:


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...............

Quoted:
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.

Quoted:
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.

Quoted:

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

Quoted:
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.

Quoted:


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.

Quoted:


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?

Quoted:


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

Quoted:

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

Quoted:


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.

Quoted:

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.

Quoted:  
I just dug mine out, the numbers are too faded to see.

Quoted:


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?

Quoted:


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.

Quoted:
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.

Quoted:


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

Quoted:
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.

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

Quoted:
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.

Quoted:
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.

Quoted:
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

Quoted:
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...

Quoted:
You know no one here has mentioned how to check your exact headspace. Anybody?........Hint........Think of headspace gauge's like feeler gauge's

Quoted:

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

Quoted:
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.