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Old July 26, 2016, 01:08 PM   #1
currancchs
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PA10 (PSA Version of AR10/LR308) Rupturing Steel-Cased Ammo and Piercing Primers

Any advice that the collective could give me on the attached pictures would be greatly appreciated.

The rifle is a Palmetto State Armory PA10, chambered in 308.

The (relevant) rifle configuration is:
-18’’ Stainless Midlength Barrel (Palmetto) with Mid-length Gas Port, chambered in 308
-SLR Rifleworks Sentry 7 Adjustable Gas Block (on setting 3/15, from fully closed – This is the lowest setting that allows bolt hold-open on last round, perhaps the rifle is over-gassed a bit?)
-Aero Precision DPMS LR-308 Style NiB BCG with Forward Assist Serrations
-H3 AR15-Length Buffer (my effort to keep the bolt locked up longer/delay unlocking/prevent bolt bounce)
-PA10 Buffer Spring/PA10 (extended to allow use of AR15 buffer weights) buffer tube
-PA10 Upper/Lower
-ALG ACT Trigger w/lighter hammer spring installed (~4.5lbs. pull) - This is basically a nickel boron coated version of the normal mil spec trigger with a lighter spring
-10 Round PMag

I have had TWO case ruptures in ~35 rounds of TULA (~110 rounds total through rifle); see attached pictures of the second ruptured case. Both cases stuck in the chamber, required a hammer/wooden dowel for removal. The first stuck/ruptured case, which I don’t have a picture of, had an ejector-shaped piece of metal removed from the case rim. I know Tula isn't the greatest, but even it shouldn’t be rupturing at this frequency…

Ejection angle is ~3-4 O’clock with brass, but 1-2 O’clock with the steel. Chamber and barrel (as well as Bolt/BCG) are thoroughly cleaned after each outing. Headspace has been checked/verified.

Case ruptures have only happened with steel, although I have previously had issues with pierced/cratered primers with this setup when shooting XM80CL brass (Perfecta 147gr and Federal Gold Medal Match 175gr. SMK work fine). I am thinking that the lighter hammer spring may be a contributing factor to the pierced/cratered primer issue.

The ruptured case in the pictures almost looks like it was unsupported by the chamber at the point where it ruptured, there is a slightly-discolored ring near the base, about 1/8’’ of the way up the case sidewall. Sorry about the poor quality of the photos, very small upload file size limit on these forums, so had to reduce quality.

The rifle was fully stripped and inspected after both case rupture malfunctions. No damage to the rifle (or my face or hands for that matter) was apparent following either malfunction.

Thanks for reading this far. If you have any suggestions (other than don't shoot crap ammo) I'm all ears. Should steel-cased ammo not be usable in this rifle, its not the end of the world and I won't use it anymore, but I'd like to understand why I'm having the issues I am as opposed to just switching ammo and not getting to the root of the issue. Obviously this ammo runs OK in other rifles, so what's the difference here?
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Last edited by currancchs; July 27, 2016 at 09:28 AM.
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Old July 26, 2016, 01:15 PM   #2
CarJunkieLS1
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Maybe TULA had a bad lot of ammo and it's over pressure...it's obviously over pressure in your rifle. Other brands of ammo shoot fine? If they do I'd see if that ammo gives the same symptoms in another rifle, if it does then I'd be contacting TULA pronto.
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Old July 26, 2016, 01:18 PM   #3
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Just a question about your PSA parts and the lower. I am looking at building one. What did you find about compatibility? I know this seems to be issue on the AR10's . Thanks
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Old July 26, 2016, 01:49 PM   #4
currancchs
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CarJunkieLS1:
Thanks, yeah, definitely seems overpressure. Unfortunately, I don't have access to another 308 for testing. I've reached out to Palmetto State Armory already and will soon reach out to Tula (and MidwayUSA, since I purchased the ammo from them) if the consensus is defective ammo. I was originally thinking tight chamber causing higher than normal pressure, which is why I first reached out to PSA instead of the ammo manufacturer, but I could certainly be wrong.

I've only shot Federal Gold Medal Match 175gr. SMK, Perfecta 147gr. and Federal XM80CL (I believe 149gr.) in this gun so far. The XM80CL was having blown/cratered primer issues, with cratering every round and pierced primers once every 5 rounds or so (only shot 15 total from the same box), which could definitely be a sign of high pressure (or a light hammer...). The other ammo shot just fine, primers a bit flattened, but not too bad, otherwise nothing unusual.

Truckeic:
The vast majority of the parts are either standard AR15 or DPMS LR308 Gen2. PSA sells an "upgrade kit" for around $20 that comes with the 4 proprietary parts on the gun, the bolt catch, magazine release and two takedown pins. I bought extras, just in case they stop making them. If you buy the upgrade kit, you can use any AR15 lower parts kit to assemble the lower.

The BCG is DPMS LR308, although you'll have to search a bit for one that has the forward assist serrations, I use an Aero Precision NB BCG.

For buffer tubes, you can run a standard LR308 buffer with the short buffer weights or the PSA version (I think its also a DPMS LR308 style), which is longer and accomodates AR15 (longer) buffer weights. I chose to go with the latter for compatability with the weights I already had.

Handguards are hit or miss, but most DPMS .150'' (low-profile tang) hanguards work. I run Midwest Industries free float handguards.

Looking back, I would suggest a rifle-length gas system in anything over 16'', as my 18'' (midlength gas system) is pretty badly overgassed, hence the barely-cracked-open adjustable gas block.

If you're interested, I could provide my build spreadsheet when I get home tonight that lists every part, cost and place of purchase. Let me know.

Last edited by currancchs; July 26, 2016 at 04:14 PM.
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Old July 26, 2016, 04:10 PM   #5
243winxb
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Another PA10 with a starting load, pressure problem. http://www.ar15.com/forums/t_6_42/46...owing_out.html

Last edited by 243winxb; July 26, 2016 at 07:40 PM. Reason: Change link
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Old July 26, 2016, 04:36 PM   #6
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Well, I wouldn't rule out steel cased ammo until you can section a couple of the normal spent cases and at least one of the bulged cases. If there is an obvious defect in the case that caused the problem, then mystery solved.

And yes, anything over 16" should have a rifle length gas system. Once you get the gas port more than 4" away from the muzzle you can run into timing issues and gas quantity issues.

The pierced/cratered primers in the XM80 ammunition is an interesting data point.

If the XM80 was surplussed off the LC line, it would have been charged with WC846 powder, aka BLC-2. It's a very temperature sensitive powder, and your gas system isn't going to do it any favors.

But, to get more data....

What is the temperature when you were shooting?
Did you let your ammo sit in direct sunlight?
How rapidly were you firing the rifle?
Do you have any pictures of the primers that were pierced/cratered on the XM80?
Have you checked for firing pin protrusion to make sure your pin isn't sticking out too far?
Do you have a heavier buffer to swap in to see if that slows things down to mitigate some of the gas issues?

I hope this helps,

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Old July 26, 2016, 05:24 PM   #7
currancchs
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243winxb:
Thank you for the link, but it is inoperative for me...


Jimro:
First off, thank you for your detailed response. I'm currently in the process of moving, so it might be a while until I get a chance to section the case (tools are packed), but I will do as you suggest and section a case as soon as I am able and upload pictures when available.

Regarding the XM80, I know from the headstamp that it was LC brass, had no idea about the powder/temperature sensitivity, but will keep that in mind in the future.

On the occasions that I've had the rifle out, its been very hot, mid-90's or so (Southern NH). The XM80 and other brass ammo was shot from a wide open field with no shade on sunny days, the steel ammo was shot on similarly hot days, the first time in direct sunlight, the second time from a covered range.

The XM80 was probably left out for ~20 minutes prior to shooting, in the box, but in pretty direct sunlight... In the future I will be looking for shade, at least for the ammo.

At the time the rifle was piercing the XM80 primers, I was loading it with between 2-5 rounds at a time (working on gas block adjustment for proper cycling) and taking my time between shots. I only shot about 12-15 shots total that day, as the two pierced primers caused me concern and I wanted to inspect the rifle prior to continuing use.

On a further range outing, where I was shooting from a covered/shaded location, but in equally hot weather, I shot ~70 rounds of mixed Federal Gold Medal Match 175gr. SMK and Perfecta 147gr. ammo without any failures, again loading about 5 shots at a time with maybe 15 seconds between shots, taking my time to reload magazines and check targets, probably took a bit over an hour to shoot the 60 rounds.

My last two outings, using the steel cased ammo were on equally hot days (why has it been so hot lately???). On the first outing I was shooting in direct sunlight in an open field with the ammo also in direct sunlight, but only for ~10-15 minutes. I only shot about 15 rounds that day before getting a round stuck in the chamber, which I had to return home to fix as I had not brought a cleaning rod/dowel or hammer... On the second outing, I shot from a covered range and shot ~25 rounds, during which time no malfunctions occurred, until the last round stuck in the chamber, ending my day. The second stuck casing (the one in the original post pictures) came out a bit easier than the first.

Firing pin protrusion is 0.0485'', but take this with a grain of salt;I used a Harbor Freight caliper to measure the protrusion

When I started test-firing the rifle, I was using the PSA-reccomended H buffer, since then, I swapped in an H2 and currently have an H3 installed. The H2 didn't seem to make much difference, but the H3 brought ejection from around 1:30-2 to ~3-4 o'clock. Not sure how informative that is...

I have attached pictures of the cratered/pierced XM80CL and of the OK Perfecta and Federal in case helpful. Some of the cases have significant ejector-swipe on them, this was from me playing with gas settings. Normal bolt holdback/cycling without ejector swipes was eventually obtained with the proper gas setting.

Thanks again to all who have read/responded!
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Old July 26, 2016, 05:25 PM   #8
currancchs
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Also, see attached for a picture of the rifle for reference.
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Old July 26, 2016, 08:45 PM   #9
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Wolf 308 was Tula, not sure if still so, and Wolf 308 had Kabooms reported several times in the past. Seems like only semi, not heard on bolt guns. Steel case tends to stick to chamber and semi is hard on the brass.
http://www.falfiles.com/forums/showthread.php?t=176323
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Old July 26, 2016, 09:42 PM   #10
currancchs
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This person seems to have been having pierced primer/overpressure signs in a similar build:
http://www.glocktalk.com/threads/psa...heavy.1573972/

He mentions a pierced primer in post #18 and just mentions high chamber pressure, without discussing the symptoms that made him think that was the case, in post #1. He also mentions 1-1:30 ejection angle and taming that with a H3 buffer and Springco Orange buffer spring as well as ejector swipes on spent casings. Eventually PSA got him a barrel that was OK.

This person also seems to have similar issues (pierced primers) with a similar build, but no case ruptures: http://www.calguns.net/calgunforum/a...t-1090810.html

Last edited by currancchs; July 27, 2016 at 04:47 PM. Reason: Added a link to another person with a similar rifle/issue
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Old July 27, 2016, 03:23 AM   #11
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currancchs,

Thanks for the additional data.

What I *think* is happening is that your rifle is experiencing high pressure symptoms in combination between a tight chamber and temp sensitive powder. The pierced primer is actually a good sign because it means the pressure spike happened while the bolt was still fully in battery, where a popped primer would mean you got a pressure spike while the bolt was out of batter (a common symptom when people shoot surplus 5.56 ammo through a 223 chamber and the ball powder produces a secondary pressure spike which translates back into the chamber just as the bolt is unlocking).

When ball powder is difficult to ignite, the initial pressure from the primer can push the bullet into the lede where it gets stuck until the powder "catches up" and you see a higher than normal pressure spike, one of the reasons why so many people recommend magnum primers for ball powders.

The Fed GMM 175gr ammunition is reportedly loaded with IMR4064 currently (it has used Re15 in the past) as it is more temp stable, both of those powder options are extruded stick powders, and are very easy to light off. The Fed match primer is very mild, and so is likely to be much less "energetic" at pushing the bullet into the lede so there is a much smoother pressure curve. I don't know what's used in the Perfecta ammunition you used, sorry.

What I recommend is you get the chamber polished and have the throat recut to a shallower lede. The headspace is fine so polishing the chamber and recutting the lede should be done by a gunsmith. This won't fix the problem of having a midlength gas system on a rifle length barrel, but it should ameliorate some of the symptoms of overpressure ammo.

I hope this helps,
Jimro
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Old July 27, 2016, 07:05 AM   #12
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"The pierced primer is actually a good sign because it means the pressure spike happened while the bolt was still fully in battery, where a popped primer would mean you got a pressure spike while the bolt was out of batter (a common symptom when people shoot surplus 5.56 ammo through a 223 chamber and the ball powder produces a secondary pressure spike which translates back into the chamber just as the bolt is unlocking)."

Un-related to the OP BUT I question this statement.
"Popped" primers can and do occur with all action types. It is not caused by residual pressure inside the case but by the case head expanding to the point the primer is loose in it's pocket and the primer falls out.
I won't even start on the description given for 5.56 in .223 pressure issues.
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Old July 27, 2016, 07:10 AM   #13
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I'm in agreement that the problem is likely related to some issue with the chamber/throat of the rifle. Something is too tight causing pressures to rise beyond safe and should be addressed before worse things happen.
ANYTIME you're seeing "ejector swipes", you'd better be taking action.
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Old July 27, 2016, 08:07 AM   #14
currancchs
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Thank you all for your assistance and recommendations. Very informative, especially the primer/powder pressure curve and temperature sensitivity issues pointed out by Jimro.

It looks like gunsmithing that is beyond my skill level will be required, so, seeing as this is a new barrel that's had issues from the first shot, I have contacted Palmetto State Armory describing the situation and am waiting for their reply. I am going to try to negotiate a 20'' barrel with rifle length gas port as a replacement, we'll see how that goes.

I'll post any updates on the situation here so that people who find this thread in the future know both what the problem was determined to be and how PSA takes care of its customers.

Mobuck:
I didn't know that ejector swipes (is there a better, more technical name for them) were such a big deal. Most threads that I read that mention tham discuss them fairly casually, almost as something to be expected on 308 semi-autos. I will certainly pay closer attention to this sign in the future though, especially with handloaded cartridges, once I get the loading equipment setup (I currently load .223 and .45ACP and have not had issues, but generally use very conservative loads). I wanted to run factory loads through this rifle for the first 500 shots or so to build up a brass supply and work out any kinks.

Thanks again everyone!
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Old July 27, 2016, 08:09 AM   #15
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Quote:
"Popped" primers can and do occur with all action types. It is not caused by residual pressure inside the case but by the case head expanding to the point the primer is loose in it's pocket and the primer falls out.
This is true. That is a case head expansion, and it is associate with a pressure event beyond a proof level load.

But specifically in an AR when normal pressure ammo loses a primer without case head expansion it is because a pressure wave bounced back into the brass case during the extraction cycle. The brass experiences a sudden increase in internal pressure, the primer backs out against the bolt face and can even push the bolt face away from the brass, causing the primer to pop out and often fall into the trigger mechanism. If this happens, there won't be case head expansion because the pressure in the brass was never high enough to expand the case head, just push out the primer. The residual pressure may also push the brass out of the rifle with a weird ejection pattern, or the brass may get stuck in the chamber.

This is often where the "don't shoot 5.56 in a 223 chamber" advice comes from, because milsurp 5.56 uses hotter primers, and ball powder (except for Radway Green, last time I pulled one of those down) which tend to push the bullet into the tighter lede on primer detonation, where it gets stuck, then the ball powder "catches up" in a locked system which starts the initial pressure spike, which pushes the bullet further down system faster than normal which causes a rapid increase in combustion volume which can then increase the surface area of all the remaining powder that goes at once causing the secondary pressure spike. And that is ignoring the pressure wave functions running through the barrel and bore for sake of a simple explanation. But, this is why recutting the lede on a 223 chamber addresses that symptom, it lets the bullet travel further on initial primer detonation which gives the powder more time to deflagrate and generate a smoother pressure curve.

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Old July 28, 2016, 08:57 AM   #16
currancchs
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Response from Palmetto State Armory

PSA has responded to my request that they inspect and/or replace the barrel with a refusal to do so, citing the variety of parts of different manufacture that the rifle was built with as the reason for their refusal to take a look at it. The action is almost entirely built of PSA factory parts, however, including: buffer tube, buffer weight, buffer spring, barrel, upper receiver, lower receiver, lower parts kit and trigger (well, its an ALG unit, but was purchased through PSA). The only (action-related) parts that are non-PSA are the gas block and BCG, which was checked for correct headspace (it was fine). I followed up with a response stating the above and am currently awaiting their reply.

Last edited by currancchs; July 28, 2016 at 11:04 AM. Reason: Grammar
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Old July 28, 2016, 09:40 AM   #17
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If PSA won't help you out, just contact a gunsmith to look through the rifle and see about a chamber polish and lede cut. The gunsmith might have a different idea what the problem is with a physical inspection.

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Old July 28, 2016, 09:56 AM   #18
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That's definitely the plan Jimro. Thanks again.
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Old July 28, 2016, 10:25 AM   #19
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OP I sincerely hope that you get your rifle figured out. Thank You for posting your experience with PSA and their CS. Makes me glad I chose a different company for my "AR-10" build. It's obvious PSA doesn't stand behind their products. BTW I'm guessing it's a barrel issue. There's no other reason it could be IMO but I'm no expert.
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Old July 28, 2016, 10:32 AM   #20
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Please keep us informed as I buy lots of stuff from PSA. I find it disturbing that they are unwilling to look at it with most of the parts coming from them...
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Old July 28, 2016, 11:20 AM   #21
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With all due respect, you built a "Frankengun" and are having issues running the "cheapest" (steel cased, not actual price) ammo in it.

Do you have any other .308 available to test the steel cased ammo in? Bolt gun?? Other semi? anything???

I understand you'd like to be able to fix the problem, and want to know what to do, to do that, other than change the ammo. But sometimes, the right answer is "change the ammo".

Semi autos are not omnivores. Some guns will run fine on a wider range of ammo than others. You can work on tuning a gun to run right on Brand X, but if you do, it might not run right on Brand A...

There is a huge number of variables at work here, and the ONLY way to track down what is going wrong is to ONLY CHANGE ONE thing at a time.

Maybe you got a bad batch of steel cased ammo. Maybe its only bad because of something in its "fit" in your rifle. Maybe its something else. You mention two loads (brass cased) that work fine. The obvious answer is that something about the steel cased loads isn't right for your gun. The exact cause may not be obvious, though.

I admit, I'm not a fan of steel cased ammo, and I do not use it. Note that the US military does not use it in our small arms. We did try it in .45acp (and possibly in .30 carbine) for ONE year, in the middle of WWII (1943, when we also made zinc/steel pennies), and returned to using brass the following year, and never went back to steel.

Other nations used steel cased ammo in their military arms, because of cost and supply considerations, primarily, and because steel cased ammo worked "well enough". Machine guns and combat rifles (especially Soviet ones) are more ..forgiving of the differences. You built what amounts to a high end target rifle, compared to belt feds and AKs, and it seems to be a lot less forgiving of steel.

I can understand the barrel maker refusing to work on your gun (for free) its NOT their gun. I don't understand why they would refuse to inspect your barrel, (which is their part) and if no defect was found they would be right in charging for that service.

One final point, would someone please explain what you mean by "ejector swipes" for those of us not up on current "lingo"???
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Old July 28, 2016, 12:25 PM   #22
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Hi 44AMP,

Thank you for your input. Definitely some valid points in there. Just to be clear though, I don't have a problem with changing the ammo, if necessary, I just wanted to get to the bottom of why I'm having case ruptures when shooting steel AND over-pressure signs in some brass without the first person chiming in and saying that steel is junk and don't run it/that's your problem. I like to understand things and will be the first to admit that I don't fully understand what is going on here. Looking back, even the brass that fired without incident had pretty flattened primers (see attachments to post #7), so I think even those commercial brass loads were overpressure for this gun.

Also, I'm not sure that I would consider my gun a "Frankengun". I mean, sure, its not 100% PSA, but the functional parts of the gun, with the exception of the BCG and gas block, are 100% PSA. What handguard, scope, stock or charging handle I run shouldn't affect chamber pressure or general function. I do agree that the BCG, if headspace was improper, could cause issues, but that has been checked and confirmed OK.

Unfortunately this is my only 308... Nothing to test with and no buddies with 308's either. Maybe in the future I'll pick up a Remington 770 or something, but nothing for now.

Also, I understand that my gun may not run all types of ammo well. I don't have a problem with a picky gun (part of the reason I got the adjustable gas block and different weight buffers was to fine tune the rifle to specific ammo). I don't consider case ruptures to be a gun being picky though, that, to me, indicates a potentially dangerous defect requiring inspection and repair, regardless of what type of ammo (assuming factory-loaded ammunition) resulted in the failure, steel-cased or otherwise.

I am also aware that steel cased ammo in 308/223 or their NATO equivalents (well, close enough) don't have as much of a taper to the case as 7.62x39, so can cause ejection issues due to less obturation (sealing) of the case to the chamber, which results in carbon fouling of the chamber, combined with steel on steel having a higher coefficient of friction than brass on steel. I would not consider steel ejection issues to be a problem that would justify PSA inspecting or replacing the barrel, just a tight gun being picky. Again, that's not the case here though. Also, the two ruptures were from different lots of steel-cased ammo, so don't think it was just a bad batch.

As an aside, I run steel cased when target shooting at 200 yards or less, unless trying to get best accuracy, because the money saved pretty easily pays for any increased wear of components over time and allows me to take the rifle out more than I otherwise would be able to.

I would agree to payment for the inspection/shipping if no defects were found in the barrel and can agree that it would not be up to the manufacturer to inspect the rifle as a whole, due to it not being assembled by them and containing other manufacturer's parts.

Lastly, ejector swipes are gouges in the rim of a case (the ejector imprinting on the case rim), which I believe are caused by hard/over-gassed/early extraction. I'm not sure where I picked up that term from and if there is another, more appropriate/universal term I should be using I would appreciate it if someone could let me know. See the second set of pictures (attached to post #7) showing the "OK brass". Some of the case rims appear OK, some have gouges/shiny spots from when I turned the gas up a bit too much. They're actually not that bad or visible in those pictures, my first time out they were quite a bit worse (I had the gas turned up a bit more I think).

Last edited by currancchs; July 28, 2016 at 12:49 PM.
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Old July 28, 2016, 09:14 PM   #23
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"but the functional parts of the gun, with the exception of the BCG and gas block, are 100% PSA."
Those two items are a BIG percentage of "the functional parts".

"Lastly, ejector swipes are gouges in the rim of a case (the ejector imprinting on the case rim), which I believe are caused by hard/over-gassed/early extraction."

"Ejector swipes" describes an incident in which high pressure causes case material to flow into the ejector recess and subsequently the flow material is "swiped" off as the bolt rotates while the case remains stationary in the chamber. Such an occurrence with steel cases would be dramatic although it has nothing to do with extractor marks which you seem to be describing.
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Old July 28, 2016, 11:25 PM   #24
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Mobuck
Re: BCG & Gas block being a big percentage of the functional parts, I agree, they are. Especially the BCG. I can see how the BCG could cause issues, not so much the gas block, assuming adequate gas flow. That being said, I can't see how a BCG that checks out on headspace could cause my issue, but I could certainly be wrong on that.

Re: Ejector swipes - I did confuse ejector swipes with extractor marks. Still learning correct terminology. Thanks for clarifying.
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Old July 29, 2016, 06:47 AM   #25
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Clearly that ammunition is too hot for that barrel. That is just the bottom line, whatever bullet, powder, case, the combination or even just one element is too hot for your barrel.

I am of the opinion you are going to have to reload for your rifle and I recommended starting below the minimum loads in the manual because you are having overpressure indications with all the factory ammunition you tested. You must have a very tight barrel. These things happen.
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