AR10 6.5 Creedmoor problems.... Need Help Bad

[1222travis]

Ok, I can't find anything about my problems, so here goes. I built a custom AR10 6.5 Creedmoor rifle from an 80% lower. It is having a major issue that is mind boggling me. It has had 68 rounds through two different barrels. First, I will list what its built of and then the confusion.

Build components:

Ballistic Advantage Match Grade 22" fluted stainless barrel
Davidson defense 308 upper
Omega MFG slim .936 gas block with rifle length stainless gas tube
Omega MFG MIL 308 buffer kit (standard)
Recoil Tech. lower parts kit
Recoil Tech. MIL 308 BCG/ changed to Davidson Defense Nickel Boron 308 BCG

Now the confusion:

First 10 rounds fired were Hornady Match 140gr ELD. Fired great and accurate. Last two rounds would not cycle ... chocked it up to need cleaned and oiled up more. Did that and a few weeks later, fired same rounds and problem started. Primers started bulging outwards towards firing pin/bolt. Fired 7 rounds and stopped. Completely disassembled and cleaned thoroughly. Bought a box of Norma Long Range hunter 142gr?? and tested. Got even worse. Where firing pin struck, primer blew out and left a hole in primer, clogging up BCG and bending firing pin holder pin. Thinking those rounds were defective, contacted Norma and purchase was refunded. Now, being an avid reloader, I figured trying a custom handload. I loaded a brand new Hornady brass with Winchester LR primer, 40.7 grain H4350 powder, Hornady 143 ELD-X bullet and seated at 2.810" COAL. Shot 3 rounds .... shot great, no problems, no issues. Let it cool, shot another 3 rounds. Blown out primers at firing pin location.????? Went home and cleaned. Tried again .... same thing .... blown primers. Tried a new upgraded BCG. It wouldn't even fire a single round. So at this point, I talk to a local gun shop. Show them my casings and they recommend taking to gunsmith. With barrel under warranty, I contact them. I sent it to them along with both my BCG's. Couple weeks later, get a response that the head space was too large and they sent me a new barrel in spec with the BCG's in spec also. So, after a few months of not being able to go out shooting, I finally did the other day. Same GD problem!!! So now I'm figuring maybe just an extremely tight barrel and need a light load. So I made some minimum light loads of brand new Hornady brass, Winchester LR primers, 38.8 grain H4350 powder, Hornady 143 ELD-X bullet and seated 2.800" COAL. Same problem, bulged primers at firing pin hit and this time not cycling a new round. Tried a round with 39.1 grain powder ... blew hole in primer but cycled rounds. Had to change BCG's because it bent firing pin holder.

So, what the hell is going on?!?! I've read on here that some people are using the same bullet load with 42 grain powder. Do I need to just buy a new barrel from different company?

 

[kilizyrag]

My guess is severely over gassed. Close off the gas and test.

 

[msgriff]

BA uses rifle length gas (RLGS) on their 22" 6.5 Creedmoor barrels. Most higher end manufacturers use +1", +1.5". or more common, +2" gas systems on that caliber and length barrel. With the shorter RLGS, the bolt unlocks with higher residual bore pressure, which can cause the primer issues described. Other than a different barrel with a longer gas system, you can try to delay the bolt unlocking with a heavier buffer. An adjustable gas block can also help.

As with most parts from Davidson/Delta/MMC/Omega (all the same company), your action/ recoil system is one of the cheapest available, with one of the lightest buffers made. No matter what you do with the barrel, upgrading your action/recoil system would be advisable. There are a couple options, the most common higher end option for collapsible stocks uses an intermediate (A5) length receiver extension (RE, buffer tube), an H3 AR-15 carbine buffer, and the appropriate action spring. There are some options that might help if you do not want to change out the RE, but I wouldn't advise them with that caliber and length barrel.

Your bolt/BCG might have the the same quality issue as your action/recoil system, as it's from that same company mentioned above. Even though it is marketed as suitable for 6.5 Creedmoor, it may not be in reality. One way to check is to accurately measure (+/- 0.0005") the firing pin tip and the firing pin aperture of the bolt face.

 

[whatsupdoc]

You put together a bunch of low end parts from various manufactures to build a rifle that has no standard.
Post some pics of the firing pin protrusion, the fact that gas is pushing the firing pin back with
enough force to bend the retainer is crazy.

I would get a better buffer system and turn the gas off, then start shooting increasing the gas
and see what happens.

 

[stanley_white]

If possible, I would sell the rifle and buy a complete rifle system, fully assembled, from a reputable manufacturer.

-Stan

 

[1222travis]

BA uses rifle length gas (RLGS) on their 22" 6.5 Creedmoor barrels. Most higher end manufacturers use +1", +1.5". or more common, +2" gas systems on that caliber and length barrel. With the shorter RLGS, the bolt unlocks with higher residual bore pressure, which can cause the primer issues described. Other than a different barrel with a longer gas system, you can try to delay the bolt unlocking with a heavier buffer. An adjustable gas block can also help.

As with most parts from Davidson/Delta/MMC/Omega (all the same company), your action/ recoil system is one of the cheapest available, with one of the lightest buffers made. No matter what you do with the barrel, upgrading your action/recoil system would be advisable. There are a couple options, the most common higher end option for collapsible stocks uses an intermediate (A5) length receiver extension (RE, buffer tube), an H3 AR-15 carbine buffer, and the appropriate action spring. There are some options that might help if you do not want to change out the RE, but I wouldn't advise them with that caliber and length barrel.

Your bolt/BCG might have the the same quality issue as your action/recoil system, as it's from that same company mentioned above. Even though it is marketed as suitable for 6.5 Creedmoor, it may not be in reality. One way to check is to accurately measure (+/- 0.0005") the firing pin tip and the firing pin aperture of the bolt face.

Wow, I never would have thought the gas system but makes total sense. I just ordered H3 buffer and spring and also an adjustable gas block. Hopefully they will work.

 

[1222travis]

If possible, I would sell the rifle and buy a complete rifle system, fully assembled, from a reputable manufacturer.

-Stan

Can’t sell 80% assembled lower.

 

[1222travis]

You put together a bunch of low end parts from various manufactures to build a rifle that has no standard.
Post some pics of the firing pin protrusion, the fact that gas is pushing the firing pin back with
enough force to bend the retainer is crazy.

I would get a better buffer system and turn the gas off, then start shooting increasing the gas
and see what happens.

 

[LRRPF52]

So you’re in the right place to get some feedback from people who have been there, done that over the past several decades with regard to AR-10s chambered in 6.5 CM and .260 Rem. I’ve been shooting .260 Rem and 6.5CM AR-10s since the 2000s, have trouble-shot a lot of them, accurized, spec’d builds with high-end manufacturers, and dealt with the issues you’re seeing.

I’ll just fire away at my initial reactions to your post and not hold any punches, so you get it straight.

Ballistic Advantage Match Grade 22" fluted stainless barrel
Davidson defense 308 upper
Omega MFG slim .936 gas block with rifle length stainless gas tube
Omega MFG MIL 308 buffer kit (standard)
Recoil Tech. lower parts kit
Recoil Tech. MIL 308 BCG/ changed to Davidson Defense Nickel Boron 308 BCG

This list of components usually is something that might fit together as a static build for photos, but I would have zero expectations for reliable or safe performance. So you can go two ways from here:

* If you want to learn to be a large frame trouble-shooter/tinkerer, you can try to polish a turd with a list of things that may or may not result in satisfactory performance, or...

* Start over with a known performer.

Going with the tinkerer route, you will need to invest in several tools that are more valuable than any of your parts, buy new major component parts, and spend some time figuring it out. I looked over every component you have listed so far, and I would not use any of them.

None of the companies you listed have any interest in producing a reliable, solid product that has been tested as part of a whole system to function safely, let alone reliably and accurately. Blowing primers is not the norm, but can happen with excess headspace and too fast of a cyclic rate.

It appears, based on pricing of the components, you wanted a more economical route, but you have inadvertently chosen a far more expensive route.

If you want a one-and-done affordable option for an extremely reliable large frame AR-10, that has a sprung firing pin, I would look at an ArmaLite. There were some great deals on them recently, but those deals seem to be gone now.

Right now, your pressure containment system, firing pin aperture, firing pin, and gas system are all out-of-whack. I personally would have zero confidence in those components doing anything other than what they have been doing for you. Even if you get a $200 Rifle Speed adjustable gas block, it would be like buying a racing-grade fuel management system for a totaled Yugo you scrounged at the scrap yard.

You need to write-off or sell off the parts you currently have, and start over. This is really a perfect example of needing a clean slate.

For a 6.5 Creedmoor large frame gasser, the barrel, chamber, and gas port NEED to be done by someone who knows what they are doing, not a monkey in a volume-based shop cranking out as many parts as possible. I have yet to see any maker defy that rule.

If you want to shoot 140gr class 6.5mm at speeds where it’s worth it, the gas system really needs to be dialed-in with correct port location, correct diameter, correct bore, rifling, chamber dims, correct gas tube, a tight-circuit Bolt Carrier with proper fitment of the bolt inside the carrier bore, and it needs to be sprung right to cycle in the happy window.

One problem we have seen when pushing longer bullets in the tighter bore is excess cyclic rate, and dropped or blanked primers. 6.5CM is not just a .308 AR-10 with a new barrel. It’s a totally different gun from an engineering standpoint because bore volume has shrunken dramatically, and the pressure curve has been elongated substantially.

It’s why I personally only like to shoot 130gr even in the .260 Rem. gassers.

Another one you could roll the dice with is a Ruger SFAR, but it needs the RifleSpeed Adjustable Gas block to get it dialed-in in 6.5CM especially. Many people have had problems with them. If I was going that route, I would see how it shoots, then if it didn’t, I would get it re-barreled to my specs. That’s probably the most affordable option right now, but still comes with risk.

That’s the $1200 range.

Next up would be the Savage MSR-10 at $1400-$1500. They already have a wide range adjustable gas block built into them, plus a spring firing pin, and overall lighter system with a mid-sized frame that feels more like an AR-15.

For 140-147gr 6.5mm loads, you will need to back off a little bit on charge weight, so where a bolt gun might shoot them at 2740fps, you will be happy with 2680fps. This is why I like 130gr going 2780-2820fps from 22-24” barrels instead. ToF is really fast on-TGT, very flat. 140s are louder when they hit though.

Feel free to reach out, as there are several here with extensive experience building, spec’ing, shooting, and loading for 6.5CM in the AR-10. Many of them have seen these same problems over the years and found solutions to them. I can tell you right now that cheap parts will not be part of those solutions though.

 

[owtlaw]

I had a similar problem. My fix was, go to a rifle length system, 7.6 oz buffer and an AGB.

 

[stevieb92]

I'd get an SLR adjustable gas block and JP Rifles 308 HP full mass bcg. That combo works well in mine.

https://slrrifleworks.com/sentry-9-set-screw-adjustable-gas-block/

https://www.brownells.com/gun-parts...mass-operating-system-complete-carrier-group/

 

[tekmann2377]

It may or may not be possible to salvage a functional rifle from your collection of parts, even if you try the gas block, buffer, etc tricks to try and get it to run.

Sometimes there can be tolerance stacking (this means still in-spec!) and function issues even with high quality parts (JP, Criterion, LW, etc). Now imagine if the components are sub-par and way out dimensionally! There is no hope!

 

[TonyAngel]

This is why it drives me crazy when people refer to the AR platform as tinker toys. Yeah, anyone can throw the parts together only to be left scratching their head when things go bad.

It's hard to tell just from what's been posted, but my knee jerk reaction would be a head spacing issue, but going to that assumes a lot.

Now you've gotta play find the problem. This first thing I'd do is narrow down the problem. First take the gas system out of the equation. Maybe loosen the gas block and slide it forward sufficiently to block off the gas port, essentially turning it into a single shot. See if the problem persists. If it does, then you probably have a headspace problem. If it doesn't, then the issue is likely with the gas and/or buffer system.

If it's the gas system either get an adjustabke gas block, better buffer system or both.

Personally, not to be offensive, but I'm thinking that you threw parts together not knowing what you were doing and wound up with a pile of crap. The smart thing to do would be to chalk the money spent up to the price of experience and go buy a good rifle.

Having the experience I have with the platform, if someone GAVE me a box containing the parts you listed for free, I'd probably put it together when I was bored, but considering it's a 6.5Cr, I'd put an adjustable gas block on it and an A5 buffer tube, so that I could use a real buffer.

 

[whatsupdoc]

You need to inspect the firing pin tip for damage and sharp edges.
The bolt hole diameter seems have too much clearance between it and the firing pin causing cratering.
Take a good close up pic of the front of the bolt with the firing pin protruding.