Failure to Extract problems

[gatordev]

Disclaimer: Anything I post in here isn't meant to disparage or blame Rainier Arms. It's genuinely meant as asking for some info, I just happen to be working with RA parts. I understand I may be asking all of the parts to do something they can't do...

So here's the breakdown of the problem I'm having. This is with a 16" Match Grade RA 308 barrel and BCG using a carbine receiver extension (and a MATEN receiver set). I'm also using HeavyBuffers.com's CAR-10 XH buffer (his heaviest). I'm still trying to figure out what spring I'm using, but have some research to complete. The MATEN/CAR-10 XH has run flawlessly on a KAC rifle, but the RA barrel is a middy length, so the gas system is a bit different.

When shooting various types of quality (and not so) ammo unsuppressed, everything functions 4.0. However, when shooting suppressed, I get regular FTE issues where the empty case doesn't clear the ejection port and ends up getting thrown back on top of the loading round, causing the whole thing to lock up, with the case pushing down on the loaded round and the bolt up against the round. The loaded round ends up getting pretty beat up and bent in the process.

My diagnosis is that the BCG is stripping the empty case before it can clear the chamber. Makes sense with the added pressure from the can. So, before I start diving into an A5 or rifle style buffer/extension, is it possible to "upgrade" extractor springs on a 308 bolt? On an AR-15/M-16, we have the benefit of putting a rubber-baby-bumper ring in there and it solves lots of problems, but I'm not aware of such a device on the 308 side. And since there is no "standard," I'm not sure we could even have one. So, any suggestions on figuring out "if" the extractor springs are "strong enough" on the bolt?

I understand this may end up resulting in an A5 system, but wanted to explore other options before going down that road/money hole.

[SINNER]

Any damage to the spent case? In particular damage to the neck or shoulder that looks like a half moon? Sounds like it's over gassed. It will drive the spent case into the ejection port. Bolt carrier is basically trying to go into battery before the spent case clears the port. Sharp recoil impulse?

[SwissyJim]

Sounds familiar. My .308, also using a RA UltraMatch 20" barrel, was having issues when I first built it. With a standard buffer setup my issue sounded just like yours. I added the Heavy Buffers setup and everything was hunky-dorey. Now that I put a SilencerCo brake on it, and shoot it suppressed, I'm right back to where I started with the issue. I have an SLR adjustable gasblock for it but don't have the time right now to swap, mainly since I have a stripped bolt on my handguard I need to drill out and I'm having way more fun running my boat and chasing shrimp. I'm about 99.9% sure it will solve the issue- my brass went from a nice 4 o'clock ejection to damn near noon o'clock (when it ejects)

[gatordev]

Any damage to the spent case? In particular damage to the neck or shoulder that looks like a half moon? Sounds like it's over gassed. It will drive the spent case into the ejection port. Bolt carrier is basically trying to go into battery before the spent case clears the port. Sharp recoil impulse?

The base of the case might have a little scrape on it, but it's mostly just scraping off the gas/soot of the blowback. However, opening (not sure I could call it the neck) has a dented opening. Not something unheard of on an auto-loading 308. Otherwise, the brass looks normal. The recoil impulse isn't extraordinary, and prone, I can still watch bits of trash get hit at 100y. I agree, it's over-gassed, but only with the suppressor.

Sounds familiar. My .308, also using a RA UltraMatch 20" barrel, was having issues when I first built it. With a standard buffer setup my issue sounded just like yours. I added the Heavy Buffers setup and everything was hunky-dorey. Now that I put a SilencerCo brake on it, and shoot it suppressed, I'm right back to where I started with the issue. I have an SLR adjustable gasblock for it but don't have the time right now to swap, mainly since I have a stripped bolt on my handguard I need to drill out and I'm having way more fun running my boat and chasing shrimp. I'm about 99.9% sure it will solve the issue- my brass went from a nice 4 o'clock ejection to damn near noon o'clock (when it ejects)

Sounds like our situations are similar. I'm not really jazzed about dealing with an adjustable gas block, not to mention the complete re-doing of some gunsmithing. If I need to buy parts, I'd rather do it by adjusting the buffering system.

[SwissyJim]

The base of the case might have a little scrape on it, but it's mostly just scraping off the gas/soot of the blowback. However, opening (not sure I could call it the neck) has a dented opening. Not something unheard of on an auto-loading 308. Otherwise, the brass looks normal. The recoil impulse isn't extraordinary, and prone, I can still watch bits of trash get hit at 100y. I agree, it's over-gassed, but only with the suppressor.



Sounds like our situations are similar. I'm not really jazzed about dealing with an adjustable gas block, not to mention the complete re-doing of some gunsmithing. If I need to buy parts, I'd rather do it by adjusting the buffering system.

I hear ya... I was sooooo happy when the Heavy Buffer setup fixed the issue the first time. Now however, I'm a little excited that if I put the adj block on, and put my original lighter buffer setup back in, I *may* be able to get some subsonic .308 to cycle the BCG. THAT would be freaking awesome, and worth the effort imo. It's a long shot, and I'm betting against it...but... worth the attempt.

[SINNER]

The base of the case might have a little scrape on it, but it's mostly just scraping off the gas/soot of the blowback. However, opening (not sure I could call it the neck) has a dented opening. Not something unheard of on an auto-loading 308. Otherwise, the brass looks normal. The recoil impulse isn't extraordinary, and prone, I can still watch bits of trash get hit at 100y. I agree, it's over-gassed, but only with the suppressor.

Out of all my .308 rifles I see very little case damage on the spent cases. My money is on excessive bolt speed like was previously mentioned. I no longer use any carbine extensions on .308's due to these very issues. They can be made to run well but perform poorly when the rifle is used in multiple configurations. If set up to run suppressed they are picky with ammo un-suppressed and likewise if set up to run without a can they beat themselves up with a can. A5 and a green Sprinco is the best compromise but honestly a rifle buffer and tube seems to be the least picky. Adjustable gas blocks cause more issues than they fix IMO. Not even getting into the fact that you still have a rifle that won't run in all scenarios unless the block is adjusted for each configuration change. Reduced gas flow even when open and decreased reliability from carbon build up has turned me off on adjustable blocks. If you are dead set on making this run with that extension I would grab a orange Sprinco spring be willing to open up that buffer and play with the weights. Regardless I think you will find that you end up with a rifle that is very picky in regards to ammo used when switching between suppressed and unsuppressed.

.308's as a whole seem to be much less forgiving in regards to switching the use of the rifle. Even my SCAR has issues with hot loads when using a can. Factory Hornady Superformance causes the exact issue you describe, and often worse. I have seen the spent case actually wind up backwards jammed on top of the round being chambered.

[gatordev]

I'm not locked into the current extension. I've asked Clint at heavybuffers.com for his thoughts and so far, it looks like an A5 is the way to go, but I'm still trying to figure out what direction to go with the buffer. As I mentioned, I'm just not excited about adjustable gas blocks, and not just for this rifle. It's great that people like theirs, but I just don't want to worry about the maintenance.

All that said, I think I'm going to be asking for some guidance on the A5 system. I'm trying to understand what the difference is between their AR-10 system and their AR-15 system. Seems like they use the same spring for either. Since this is going on a MATEN, which takes AR-15 components (well, mostly), I need to do some more googling.

.308's as a whole seem to be much less forgiving in regards to switching the use of the rifle. Even my SCAR has issues with hot loads when using a can. Factory Hornady Superformance causes the exact issue you describe, and often worse. I have seen the spent case actually wind up backwards jammed on top of the round being chambered.

This is exactly what was happening to me. Case was primer-in, on top of the fed round. At least I have a direction to go forward with.

[gatordev]

Thanks to Slash/Clint at Heavybuffers.com, the problem seems to have been resolved with an A5 extension and some goodies from HB.com. I ran some crap PPU and some M118LR clone rounds, and no failures both unsuppressed and suppressed.

[SwissyJim]

Thanks to Slash/Clint at Heavybuffers.com, the problem seems to have been resolved with an A5 extension and some goodies from HB.com. I ran some crap PPU and some M118LR clone rounds, and no failures both unsuppressed and suppressed.

Awesome news. I'll keep it in mind if the adjustable block doesn't pan out. Only reason I am trying that first is I really wanna try subsonic loads. If in fact mine is so far overgassed, maybe.. just maybe... sub loads will cycle with all the lightest parts installed. Then I can tune it down with the block for unsuppressed work. But... if that does not pan out (not holding my breath) then I'll most likely pursue the same outcome you ended up with.

[gatordev]

My only other complaint was that I appear to have a pretty massive POI shift (.6 mil up), but it was consistent so not the end of the world. I'll probably just slip the turrets and keep the zero for running suppressed.

[SINNER]

If you get a chance could you measure the length of that buffer? Thanks

[gatordev]

I'll try the next few days.

[jbjh]

Thanks to Slash/Clint at Heavybuffers.com, the problem seems to have been resolved with an A5 extension and some goodies from HB.com. I ran some crap PPU and some M118LR clone rounds, and no failures both unsuppressed and suppressed.

What else besides the A5? New buffer/spring combo?

Thanks

[gatordev]

Correct. The XH Carbine buffer and the AR-10 rifle buffer spring.

[SINNER]

So he is providing a standard AR15 carbine buffer to use in a A5 receiver extension? No need to measure the buffer if that's the case.