6.5CM AR10 Issue

[Larry DESANTIS]

I have an AR10 built with a high end barrel I won't name right now, but it has had failure to feed, cycle etc. issues since it was installed. Headspace is ok. After trying everything in my tool box, I sent it to a gunsmith. He says that the "factory" ammo I sent him to test was too long for a gas gun. I checked and its has the standard COAL of 2.180". In my mind that's a problem with the chamber. Please correct me if you have other thoughts. PS. I really don't want to handload shorter COALS for an AR.

 

[joshb]

What was “too long”? Base to shoulder? Base to ogive? What “factory ammo”?
Who chambered the barrel?
Who built the gun?
Who tested the gun before you bought it?

 

[TxBowHunter409]

What was “too long”? Base to shoulder? Base to ogive? What “factory ammo”?
Who chambered the barrel?
Who built the gun?
Who tested the gun before you bought it?

All good questions

 

[mic2377]

I assume by 2.180 OAL you mean 2.810 OAL? Generally a AR10 in 6.5 CM would have a standard SAAMI chamber, which can accommodate 140 gr class bullets at an OAL of 2.810.

The chamber, freebore, and resultant headspace may be a completely separate issue from whether or not a semi auto runs reliably.

 

[Coyotefurharvester]

Does it matter which side of the mag the round is coming off from? Asking because you stated headspace was ok, and using factory ammo.

 

[ebb]

A friend gave me a bunch of 308s he had and wanted to shoot out of his Winchester 88. He and I both had no idea why they would not feed. I asked if he had any that would feed and he handed me a box of Winchester factory loads. After measuring I found that Winchester loaded anything that would be a good load to shoot in a lever action shorter than was standard. When I bumped the handloads back to the size of the factory ammo they chambered just fine. While you may want to not load shorter COAL, you may have to,to get it to function.

 

[Steve Donlon]

Also what bullet? Could be your set up with the springs and timing. Could be the shape of the bullet, if it's to pointed, it could be to long to feed right. Need to try different ammo and bullet weights and profiles.

 

[Canuckienns]

Built several. 6.5 CM is not plug and play as in an Ar10 platform. PP 308 is (mostly). You need a high pressure bolt ( the one with the small firing pin hole ) for magnum small rifle primers. A standard spring and buffer weight will not work successfully a lot of the time. And yes, an adjustable gas block. Ask me how I know.

 

[Coyotefurharvester]

Tubbs flat wire spring, on the heavy side buffer, adjustable gb.

 

[10XSHOOTER]

What is the failure to feed? Could be a magazine problem.
Can you single feed and have the gun fire?
Does it eject?
Are you using small rifle primers or large as you should be?
No adj gas blocks. you need all the gas to get that heavier bolt to move!

 

[Canuckienns]

What is the failure to feed? Could be a magazine problem.
Can you single feed and have the gun fire?
Does it eject?
Are you using small rifle primers or large as you should be?
No adj gas blocks. you need all the gas to get that heavier bolt to move!

wrong wrong wrong

 

[Canuckienns]

Tubbs flat wire spring, on the heavy side buffer, adjustable gb.

You got that right. 65 CM are not plug and play,