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Posted: 3/25/2019 3:21:19 PM EDT
[#1]
Edit: sorry I typed a huge answer about how headspace is checked/measured/done in an AR only to realize it wasn't even your actual question.
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Posted: 3/25/2019 4:10:20 PM EDT
[#2]
Yes, you could be stuck with a useless bolt.
Criterion uses DPMS bolts, if I remember correctly. My PA-10 bolt seems to work fine with my Criterion. |
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Posted: 3/25/2019 5:11:15 PM EDT
[#3]
Quoted:
if my setup is out of spec, is there anything I can do or am I stuck with a useless bolt? in the first instance, i had it close on a no-go, so I tried different bolts, found one that didn't close on the no-go, and then checked the GO gauge and it was ok. in a more recent instance, it wouldn't close on a go-gauge, so I tried the bolt from the earlier instance mentioned above, and it closed on the go-gauge, and I checked that it didn't close on the no-go, and it didn't. yes, I have extra bolts on hand, but sometimes I want to use a nitride and I don't have nitrided ones on hand, or similarly with a NiBo. I sometimes buy a couple extra bolts (brand names only) when they're deeply discounted, e.g. Black Friday, or clearance priced. "spend money to save money" (it doesn't work). |
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Posted: 3/25/2019 6:05:11 PM EDT
[#4]
When the factory assembles one they headspace checking with a gauge, not all factories pair a bolt to one specific barrel. They run hundreds thru and have them on hand - so checking a specific bolt that won't go means grabbing another from the next sorted bin that will work. Easy for them, not so much for us. We don't have bins filled with bolts marked for size.
Stoner did things to make it super easy on the assembly line and to cut payroll - you don't need the expensive gunsmiths doing all the work, you hire a trained assembler for that one job. It's all because the barrel extension screws on, so they get to "micrometer" adjust it and pin it in place, rather than pressing a barrel into a trunnion and getting it within a few thousandths. Major difference. Major cost cutting not having to press them, too, no presses needed, none on the factory floor. Note how many AR businesses there are out there - they aren't that hard to start up because they don't have a large capital investment in machinery. Its cheaper to assemble AR's than AK's by a significant margin. That savings in overhead is their profit margin giving them a market advantage. Unlike 5.56, .308 AR's are a much more non standard as there is no US milspec to follow. It's proprietary to a brand, so, yeah, I'd be real careful about which bolt and barrel you mate and what origins it had. |
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Posted: 3/25/2019 6:42:12 PM EDT
[#5]
Quoted:
Lastly, if my setup is out of spec, is there anything I can do or am I stuck with a useless bolt? Personally, I think it is a non-issue. Headspace is set when the barrel is machined and checked at the time of assembly. All this is done by machine operators with plenty of experience, assuming you bought from a reputable manufacturer. |
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Posted: 3/25/2019 7:55:46 PM EDT
[#6]
Just get the gauges and check. It's always a good idea. I have never had one not work, using for DPMS BCG in ArmaLite barrels even, But it doesn't hurt to check I might hurt if you're out. Everyone lets a goat escape every once in a while.
As a side note I remember in the Army our squad would do assembly line cleaning of our rifles. I remember taking like six bolts down to the latrine and washing them in the sink in hot soapy water. I'm pretty sure no body got their specific bolt back. I don't recall there ever being a failure. Of course this was M-16 A2s |
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Posted: 3/26/2019 3:18:20 AM EDT
[#7]
"As a side note I remember in the Army our squad would do assembly line cleaning of our rifles. I remember taking like six bolts down to the latrine and washing them in the sink in hot soapy water. I'm pretty sure no body got their specific bolt back. I don't recall there ever being a failure. Of course this was M-16 A2s "
This worked because the bolts were cut to a single specification, and the bbls were too. In the case of AR-10, SR-25, etc., there isn't an agreement or single design spec, so it doesn't work out the same statistically. Sometimes you may find a bolt that works with your chamber, and sometimes not. One way to make sure is to get the bolt from the same source as the one that chambered the bbl, or ask them which bolt dimensions they had in mind and pair up to those. |
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Posted: 3/26/2019 4:36:41 AM EDT
[#8]
What gauges would he need for such a chamber?
Just the std 243/308 gauges? |
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Posted: 3/26/2019 5:25:14 PM EDT
[#9]
Is it absolutely necessary to use both guages or would I "probably" be okay if I just buy a no-go guage and go from there? I really dont want to spend $60 on guages I'll probably never use again.
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Posted: 3/26/2019 5:42:02 PM EDT
[#10]
I have a Faxon Firearms barrel on my .308. It closed on the no go, but according to Faxon, that it not uncommon and does not mean unsafe or that the rifle will not be accurate. I have gotten MOA out of 200 yards thus far with it. As long as you can not close on a field gauge, you will be ok.
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Posted: 3/26/2019 6:09:52 PM EDT
[#11]
Quote HistoryQuoted:
I have a Faxon Firearms barrel on my .308. It closed on the no go, but according to Faxon, that it not uncommon and does not mean unsafe or that the rifle will not be accurate. I have gotten MOA out of 200 yards thus far with it. As long as you can not close on a field gauge, you will be ok. |
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Posted: 3/26/2019 6:12:17 PM EDT
[#12]
Quote HistoryQuoted:
Is it absolutely necessary to use both guages or would I "probably" be okay if I just buy a no-go guage and go from there? I really dont want to spend $60 on guages I'll probably never use again. |
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Posted: 3/26/2019 9:05:54 PM EDT
[#13]
Quote HistoryQuoted: I'll loan you mine if you pay shipping both ways. |
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Posted: 3/26/2019 9:30:50 PM EDT
[#14]
I don't know what Mk318 Mod 1 is and yes i do shoot 5.56 X 45 mm in rifle matches, but you keep your boolets and I'l send you my chamber gauges. Might be a few days as the barn roof caved in here from the heavy snow (34 inches measured on the roof.) PM me your addy
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Posted: 3/26/2019 9:34:53 PM EDT
[#15]
Quote HistoryQuoted:
I don't know what Mk318 Mod 1 is and yes i do shoot 5.56 X 45 mm in rifle matches, but you keep your boolets and I'l send you my chamber gauges. Might be a few days as the barn roof caved in here from the heavy snow (34 inches measured on the roof.) PM me your addy PM incoming. Thanks again! |
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Posted: 3/28/2019 2:44:36 AM EDT
[#16]
Nice!
I’m in the same boat, order the gauges and have them for maybe another build or just roll on as I’ve done for many 556 builds.. |
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Posted: 3/29/2019 8:47:30 PM EDT
[#17]
Quote HistoryQuoted:
Unlike 5.56, .308 AR's are a much more non standard as there is no US milspec to follow. It's proprietary to a brand, so, yeah, I'd be real careful about which bolt and barrel you mate and what origins it had. Improper headspace can cause a kaboom. |
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Posted: 3/29/2019 9:10:49 PM EDT
[#18]
Quote HistoryQuoted: ^ this. This is the reason why checking headspace is more critical when building a .308 AR from a mix of parts. Improper headspace can cause a kaboom. |
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Posted: 3/30/2019 12:25:48 AM EDT
[#19]
Quote HistoryQuoted: This isn't a question of weather headspace should be checked on a 308 AR, I just wanted to know what I can do if it's out of spec. If for example, a gunsmith is engaged and the reamer is available, they could bring the chamber to spec if it has too much material and needs to be cut. When too much is already missing, there are a few tricks they can pull that shorten the chamber or a shallow bolt face that can also work, within limits. This is when it is good to know a good smithy. |
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Posted: 3/30/2019 12:31:35 AM EDT
[#20]
Quote HistoryQuoted: The direction or polarity matters. Taking material off is one thing, not having enough in the first place is another. If for example, a gunsmith is engaged and the reamer is available, they could bring the chamber to spec if it has too much material and needs to be cut. When too much is already missing, there are a few tricks they can pull that shorten the chamber or a shallow bolt face that can also work, within limits. This is when it is good to know a good smithy. |
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Posted: 4/7/2019 2:30:15 PM EDT
[#21]
To update this thread, TheEarloSammich borrowed me his 308 Match headspace guages. The GO is 1.630" & NO GO 1.634"
The only ammo I have on hand is Hornady Black 168gr Amax 308 and they chamber fine but were very hard to eject the first couple. I scrubbed the chamber and they eject much easier now. When I try to chamber the GO guage it doesnt fully seat, this is just by hand, not using the spring to slam it home. I can see the lugs on the bolt turn just a little but not enough to lock the bolt or fully seat. Remember, these are 308 guages and my barrel is a Rainier Arms Match that has a proprietary modified 308 chamber, from what I understand its similar to the 223 Wylde idea. Am I stupid to think I'm safe shooting this thing? Or should I send the barrel back to Rainier and have the headspace and sell me a new bolt? |
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Posted: 4/7/2019 3:37:34 PM EDT
[#22]
Probably a stupid question, but did you disassemble the bolt before using the gages?
And, if it’s like the 223 wylde, the gage won’t show any difference, because the difference between chambers is the the throat/leade. |
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Posted: 4/7/2019 3:39:45 PM EDT
[#23]
Quote HistoryQuoted:
Probably a stupid question, but did you disassemble the bolt before using the gages? |
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Posted: 4/7/2019 7:13:40 PM EDT
[#24]
You said in one of your posts, or maybe it was a PM that you chambered a round and extracted/ejected it but it was kind of hard or difficult to get the changing handle back. Did you have to mortar it ie slam the stock down on the floor while pulling back on the charging handle? Are there any detectable marks on the ojive of the bullet in those rounds, like would come from being in contact with the lands? Any other marks in the brass? Take a round and color it up with a Sharpe and chamber it. Eject it and see where it wipes off.
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Posted: 4/7/2019 7:58:52 PM EDT
[#25]
Quote HistoryQuoted:
You said in one of your posts, or maybe it was a PM that you chambered a round and extracted/ejected it but it was kind of hard or difficult to get the changing handle back. Did you have to mortar it ie slam the stock down on the floor while pulling back on the charging handle? Are there any detectable marks on the ojive of the bullet in those rounds, like would come from being in contact with the lands? Any other marks in the brass? Take a round and color it up with a Sharpe and chamber it. Eject it and see where it wipes off. I'll try the marker trick when I get home. I didnt notice any marks on the bullet like it contacted the rifling but I also didnt look very closely. |
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Posted: 4/8/2019 4:06:53 PM EDT
[#26]
I colored a bullet black with marker, loaded and ejected it. There are scratches on the bullet but nothing that looks like it contacted the rifling.
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Posted: 4/8/2019 4:32:01 PM EDT
[#27]
Quote HistoryQuoted:
I colored a bullet black with marker, loaded and ejected it. There are scratches on the bullet but nothing that looks like it contacted the rifling. Checking headspace is another. You're trying to see if the there's a gap between the chamber shoulder and the cartridge shoulder when the cartridge is chambered with bolt locked up. If the gap is too large, the brass case will stretch to fill the void. Too much, and the case lets go just forward of the case head. I do not know of a way to check this without gauges unfortunately. |
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Posted: 4/8/2019 4:51:53 PM EDT
[#28]
What guages would be correct for a hybrid 308/762 chambers?
762 guages or? |
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Posted: 4/8/2019 6:07:53 PM EDT
[#29]
Quote HistoryQuoted:
What guages would be correct for a hybrid 308/762 chambers? 762 guages or? |
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Posted: 4/8/2019 6:36:34 PM EDT
[#30]
If I had a Criterion hybrid chamber, I'd use a JP high pressure bolt. Kreiger only recommends JP bolts for their semi-auto 308 and creedmoor barrels. Kreiger makes Criterion barrels.
I would call Rainier Arms and ask their tech support people which bolt they recommend for their match chambered barrel. If they won't recommend, ask what gauges you should use to check headspace. OP, your chamber sounds fine. You cleaned the chamber and you had less resistance ejecting a round. You weren't jamming the projectile into the lands so it's not a short throat issue. There's almost always cutting oil in a new barrel chamber and on occasion tiny bits of steel. Swab it clean, spray it out, dry it, and try again. If it's short-chambered I think you'll know. The bolt won't lock up. |
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Posted: 4/8/2019 8:12:20 PM EDT
[#31]
Those gauges you got are .308 Winchester so they are already shorter than 7.62 X 51 NATO. by `13 thou. (I would guess. Never miced them myself.)
Did you notice any coloring come off on the shoulder of those rounds, just below the neck? |
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Posted: 4/8/2019 9:02:29 PM EDT
[#32]
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Posted: 4/8/2019 9:03:18 PM EDT
[#33]
Quote HistoryQuoted:
Those gauges you got are .308 Winchester so they are already shorter than 7.62 X 51 NATO. by `13 thou. (I would guess. Never miced them myself.) Did you notice any coloring come off on the shoulder of those rounds, just below the neck? |
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Posted: 4/8/2019 10:55:26 PM EDT
[#34]
Quote HistoryQuoted:
http://i.imgur.com/8guUt9j.jpg Where are those horizontal marks on the ogive coming from? They appear to be spaced around the circumference as if the bullet is in the lands. If so, that barrel may be short throated. |
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Posted: 4/8/2019 11:50:45 PM EDT
[#35]
Quote HistoryQuoted: The longitudinal scratch is normal. Where are those horizontal marks on the ogive coming from? They appear to be spaced around the circumference as if the bullet is in the lands. If so, that barrel may be short throated. |
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Posted: 4/9/2019 7:02:27 AM EDT
[#36]
Quote HistoryQuoted:
I've never checked headspace or hand loaded any ammo in over 10 years and ~two dozen "builds" and I can't say for certain, this subject is pretty new to me in all honesty. If thats what it looks like, that's probably what it is. Do I shoot it and let it wear a bit or? Quote HistoryQuoted:
Quoted: The longitudinal scratch is normal. Where are those horizontal marks on the ogive coming from? They appear to be spaced around the circumference as if the bullet is in the lands. If so, that barrel may be short throated. As to the bolt issue, I'd still contact Ranier and ask them. That said, if the factory round is contacting the lands after being chambered then you may be sending the barrel back. It's just hard to tell with one photo. FYI, jamming a projectile into the lands isn't necessarily terrible, but it does increase chamber pressures. |
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Posted: 4/9/2019 10:15:38 AM EDT
[#37]
As The Dude said it looks like the ojive may be making contact into the throat. Also it's evident that the shoulder of the brass is taking a hit. Mark that up as well again.
What ammo is that, that you are using? My two cents is it would probably work but if you got some 7.62 X 51 NATO ammo you may be into a feeding reliability concern area. Another .006-.010 with the reamer would make it better for those who don't reload. I have shot VLDs seated into the lands but they have to be just kissing. I normally shoot SMKs .030 off the lands. Pressing the brass into the chamber is a reliability issue. Did you find out if your buddy had one of those Stoney Point/Hornady OAL guages? Did you contact Rainier yet? |
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Posted: 4/10/2019 10:01:52 AM EDT
[#38]
Quote HistoryQuoted:
As The Dude said it looks like the ojive may be making contact into the throat. Also it's evident that the shoulder of the brass is taking a hit. Mark that up as well again. What ammo is that, that you are using? My two cents is it would probably work but if you got some 7.62 X 51 NATO ammo you may be into a feeding reliability concern area. Another .006-.010 with the reamer would make it better for those who don't reload. I have shot VLDs seated into the lands but they have to be just kissing. I normally shoot SMKs .030 off the lands. Pressing the brass into the chamber is a reliability issue. Did you find out if your buddy had one of those Stoney Point/Hornady OAL guages? Did you contact Rainier yet? My buddy is in the middle of selling his house and moving a couple hours away right now so I haven't even bothered to ask. I'll try to give Rainier a call today and see what they have to say. I made the mistake of cerakoting my barrel black so I voided the warranty I'm sure but maybe they can still find a bolt that works with it. @TheEarloSammich shoot me an email with your address again, I'm going to try and get to UPS today before this supposed 18" of snow hits us and ship your guages and some ammo back to you. |
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Posted: 4/10/2019 3:17:57 PM EDT
[#39]
I emailed Rainier and am waiting to hear back from them.
A local store had Norma Match 308 168gr SMK ammo on sale today for $18/box so I picked up 100 rounds of it. This ammo is much less sticky than the Hornady ammo, it's easier to eject a live round. I colored a round of the Norma with a marker and loaded it by letting the bolt slam forward. The case shoulder shows contact still, as does the ogive of the bullet in the lands although not as bad as the Hornady. Although I don't have the gun anymore I seem to remember my Palmetto PA10 308 w/20" stainless barrel left similar marks on live rounds that were ejected. That particular rifle was surprisingly extremely accurate but equally overgassed. I never bothered to check headspace on that gun since I bought it as a complete upper and later a complete lower. |
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Posted: 4/11/2019 4:59:32 AM EDT
[#40]
Huh...so your having about the same deal as I am..
Here’s a thread I have going at ...Weapon evolution Snippet... Ok.. busy day and got the barrel and guages today, but snuck out to play once everyone was asleep.Follow along to what looks like a slightly tight chamber.. Ok , using a slightly used Rainier arms barrel with hybrid chamber and brownells/supposedly toolcraft nitride bcg/bolt. The guages are Clymer .308 win , go guage is 1.630 and No Go is 1.634 Barrel was cleaned and cleaned again. As was the Bolt , which was stripped down. Upper is not assembled, checking before hand. Insert the Go guage and the bolt will not rotate, starts to but not all the way , put bolt into bcg and try again.It begins to turn but not all the way. Does not close on the No Go...So I was curious so if grabbed some ammo. Inserted a fresh .308 -federal 165gr and the bolt turns on it. Like butter. Throw in a newish LC 762 150gr rd and it turns but with some resistance.. Not a lot but it’s not butter.. Colored up each of them with a sharpie , in and out a bunch times, rotating bolt. They both are hardly even scuffed. My pic sux as it looks screwy thru the pic. but it’s clean..but no gouges or scrapes like it was on the lands... So appears to be on the tight side..whatcha think? |
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Posted: 4/11/2019 6:00:03 AM EDT
[#41]
Could you get away with one gauge, or should I buy a Go and No Go gauge? What about the Field gauge?
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Posted: 4/11/2019 12:43:27 PM EDT
[#42]
Quote HistoryQuoted:
Huh...so your having about the same deal as I am.. Here’s a thread I have going at ...Weapon evolution Snippet... Ok.. busy day and got the barrel and guages today, but snuck out to play once everyone was asleep.Follow along to what looks like a slightly tight chamber.. Ok , using a slightly used Rainier arms barrel with hybrid chamber and brownells/supposedly toolcraft nitride bcg/bolt. The guages are Clymer .308 win , go guage is 1.630 and No Go is 1.634 Barrel was cleaned and cleaned again. As was the Bolt , which was stripped down. Upper is not assembled, checking before hand. Insert the Go guage and the bolt will not rotate, starts to but not all the way , put bolt into bcg and try again.It begins to turn but not all the way. Does not close on the No Go...So I was curious so if grabbed some ammo. Inserted a fresh .308 -federal 165gr and the bolt turns on it. Like butter. Throw in a newish LC 762 150gr rd and it turns but with some resistance.. Not a lot but it’s not butter.. Colored up each of them with a sharpie , in and out a bunch times, rotating bolt. They both are hardly even scuffed. My pic sux as it looks screwy thru the pic. but it’s clean..but no gouges or scrapes like it was on the lands... So appears to be on the tight side..whatcha think? |
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Posted: 4/11/2019 4:56:29 PM EDT
[#43]
You should not just follow, but sign up over there...good forum
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Posted: 4/11/2019 5:46:10 PM EDT
[#44]
Quote HistoryQuoted:
You should not just follow, but sign up over there...good forum |
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Posted: 4/11/2019 5:47:14 PM EDT
[#45]
Quote HistoryQuoted:
Could you get away with one gauge, or should I buy a Go and No Go gauge? What about the Field gauge? |
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Posted: 4/11/2019 6:00:37 PM EDT
[#46]
Quote HistoryQuoted:
Could you get away with one gauge, or should I buy a Go and No Go gauge? What about the Field gauge? You need to know if the chamber if is indeed to short or too long..can’t tell with one guage Dub ya- did rainier call you back? I’m trying to find a local Smith with a finish reamer, it’s so close but want it a little loiser for 762 and other possibly longer rounds.. |
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Posted: 4/11/2019 8:16:06 PM EDT
[#47]
Won't close on a Go gauge. Chamber is too short for bolt.... marginally.
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Posted: 4/12/2019 12:59:01 PM EDT
[#48]
Quote HistoryQuoted: Simple answer .. N You need to know if the chamber if is indeed to short or too long..can’t tell with one guage Dub ya- did rainier call you back? I’m trying to find a local Smith with a finish reamer, it’s so close but want it a little loiser for 762 and other possibly longer rounds.. I'd be fine if my gun shot 308 but not 7.62. I have a feeling these Rainier chambers are like this by design (for accuracy?), seems like there are plenty of threads out there where people are having chamber issues with their 308 barrels. |
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Posted: 4/12/2019 2:08:02 PM EDT
[#49]
As I said earlier I'ld touch a few rounds off. Give it a go. Fire one round and closely examine the brass. It will tell you if your getting high pressure signs. Post up some pictures of the once fired brass. especially about the base and head stamp area/primer area.
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Posted: 4/12/2019 3:19:20 PM EDT
[#50]
Quote HistoryQuoted:
As I said earlier I'ld touch a few rounds off. Give it a go. Fire one round and closely examine the brass. It will tell you if your getting high pressure signs. Post up some pictures of the once fired brass. especially about the base and head stamp area/primer area. PM me your address again, I'll get your guages and some ammo on its way to you. |
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