6.8 spc accuracy issues

[plinkin]

My brother is having accuracy issues with a ar 15 6.8 spc build, build consists of a 80 percent lower, timney drop in trigger, rock river upper, 18"1:11 wilson combat barrel, adjustable gas block, cant remember the carrier group,gen 2 pst 2-10, vortex ar mount.


Anyway when he first started shooting he was able to get .75 moa fairly consistently, after 1-2 boxes of hornady it seemed to start to open up, while shooting at 200 yards it slings shots and groups 14 inches with the same type of ammo, 120 sst hornady custom.


So we've checked the scope and mount torque as well as put it on my bolt gun with no issues, cleaned the barrel with no change, disassembled and could not find any issues torqued barrel at 80 ftlbs after reassembly the same issues. He has adjusted the gas block but other than that no changes.



What else should we look for? We plan on getting a couple more different types of ammo to check it but after that we're running out of ideas. Thanks

 

[BoulderE89]

This may be a dumb suggestion but since I can’t see the rifle, is anything attached to the handguard contacting the barrel?

 

[plinkin]

No, the only thing touching the barrel is the gas block. He has a bcm hand gaurd which fits VERY tight to the reciever barrel nut. I think it's a 1/16 of an inch gap where the closest thing that will touch the barrel and handgaurd is.

 

[digitalshooter]

You said he was using the same type of ammo. Was he using the same exact ammo or did he change the ammo to something similar?

You might want to back off the torque on the hand guard. I know technically 80 ft lbs is still in spec but it's the upper limit and I'm not sure how many people actually torque out down that much. Might be bad for a precision gun.

 

[plinkin]

You said he was using the same type of ammo. Was he using the same exact ammo or did he change the ammo to something similar?

You might want to back off the torque on the hand guard. I know technically 80 ft lbs is still in spec but it's the upper limit and I'm not sure how many people actually torque out down that much. Might be bad for a precision gun.

It's the exact same ammo that he started with, not the same lot but the same brand and bullet. Do you think 50ftlbs would be good?

 

[digitalshooter]

If the barrel nut needs to be timed I usually just hand tighten it close to where it needs to be and then finish it off to where it's properly timed. There are a couple of others like Padom that build many more precision ARs that I do and might have a different build philosophy than I do.

 

[Forward543]

You have a build issue. Take it apart and rebuild it. 14" groups at 200 are terrible no matter the ammo manufacturer. Tough to say exactly what, but most likely something loose or binding. Internet has a thousand ideas on how to improve.

 

[Gunmaster45]

Let me ask you this. How do you find the center of your group?

 

[plinkin]

Let me ask you this. How do you find the center of your group?

Lmao, I knew as soon as I saw the username lol.

 

[plinkin]

I think I figured it out.

 

[Rocketvapor]

Since there are 150 parts in the gas system that might cause this
Flip the gas block. Eliminate ALL gas function.
Just think of the Bandwidth you will save.
Then shoot some groups.