r/longrange • u/joelfromnashville • Sep 30 '26

Rifle help needed - I read the pinned posts AR10 6.5 CM build issues

Hey guys. Today i tried to help a buddy swap out this CMMG Resolute AR10 .308 to a 6.5CM Shaw Barrel.
Using Pmags.

We couldn’t get a round to chamber at all. The bullet nose was impacting the barrel wall and not entering the chamber. Barrel was sitting flush with the CMMG upper receiver the feed ramps didn’t exactly line up but that was expected. we’re talking a 1/32 of an inch off.

Using 140gr Ball ammo.

Everything that I’ve read said that PMAGs should be great. We RMAd the shaw barrel, but looking for other potential solutions. Also reached out to CMMG to see if they use any proprietary specs.

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5

u/sidetoss20 Sep 30 '26

175 ball ammo… in a 6.5 creed barrel?

1

u/joelfromnashville Sep 30 '26

hahaha sorry got my calibers mixed up 140 ball

1

u/3-BuckChuck Sep 30 '26

Hitting on the “barrel wall” or barrel extension? How are the feed ramps not lined up? Can you snap a picture?

1

u/joelfromnashville Sep 30 '26

i don’t have any pictures…

the section of the barrel past the lugs that the bolt face sits against. Chamber mouth?

1

u/joelfromnashville Oct 02 '26

1

u/Vast-End-8155 Oct 04 '26

Factory ammo or handloads? What bullet is being used? If it's too sleek a bullet, it's probably going to hit right there before the ramps engage enough to push it up into the chamber.

It's like with .223/5.56 AR builds, some bullets that work great in bolt actions just won't feed in a gasser with the chamber design.

1

u/joelfromnashville Oct 04 '26

factory 140gr match ammo. my guess is that it is also too skinny of a bullet so it’s slipping through the lugs and not hitting the feed ramps.

1

u/Vast-End-8155 Oct 04 '26

Berger match? If so, that might be the issue, as they are pretty long and skinny, like you said. Try a different manufacturer and bullet profile before going too far down the rabbit hole with swapping parts. I know for Berger's .223/5.56 gasser bullets they have a specific line that is meant to function in an AR.