AR-10 issues

[Slow Hand]

I went back and forth on whether this would fit better in Rifles, Anmunition, or GunSmithing as it involves all three...


I assembled a .308 AR-10 this summer. I was finally able to get it out Shooting a couple months ago. With 7.62 NATO 147 gr ammo it runs perfect. With my handloads that are basically 168 FGGM copies it appears to be overgassed. I am shooting it suppressed the majority of the time and that is the plan. I sjot it again a couple weeks ago and it ran fine unsuppressed with the 168’s and also suppressed and unsuppressed with the 147 NATO ammo.

Last night I installed a JP adjustable gas block. I test fired a few rounds tonight. I closed the adjustment screw all the way down and then opened up one full turn as suggested in the installation instructions. I tried it with one round in the mag. Fired ejected and locked the bolt back. I screwed the adjustment screw in one half turn and tried again. Fired, ejected but bolt closed on an empty mag. Opened the screw 1/4 turn. Fired ejected and locked back on empty. I then tried it with two rounds in the mag and it worked as it should.

All seemed well well until I picked up the empty cases and saw ejector marks on three of them. It may be awhile until I can make it to the range for a real test fire so I figured I’d check with you guys to see if you and any experience with this. I have not seen the ejector swipe before installing the gas block. I know the case head swipe can be caused by high pressure and/or timing issues. I

I went with the adjustable gas block over changing buffer and spring weights as I figured it was a more ‘proper’ solution.

 

[Slow Hand]

View attachment 60669

 

[Vigilant]

Did you pay attention to the ejection pattern?

 

[Slow Hand]

Did you pay attention to the ejection pattern?

Not or on the test fire. The test location doesn’t lend itself to that. More of a function test...

 

[NyleRN]

Definitely very odd it's happening only after the adjustable gas block install. Or so you think. The timing of your bolt may be off. Possibly unlocking too early causing those swipes. If I were you I'd be inclined to try a sprinco orange spring and then set the adjustment using the same metbod as before then check your brass

 

[Slow Hand]

Definitely very odd it's happening only after the adjustable gas block install. Or so you think. The timing of your bolt may be off. Possibly unlocking too early causing those swipes. If I were you I'd be inclined to try a sprinco orange spring and then set the adjustment using the same metbod as before then check your brass

I have ave the vast majority of the brass I fired through it in the two original trips and non show similar marks. I am thinking of getting a Tubb Flat spring and trying it out.