All,

Currently breaking in the barrel on my PRI MK12 MOD 0 , and seeing some pretty poor accuracy with black hills mk262 OTM (about 1.5 - 2 inch groups at 100 meters).  For a comparison - I have a knights LPR with an 18 inch kreiger barrel, and that rifle with the same ammo shoots sub half MOA if I do my part.  Last 10 shoot group I printed with the knights was .77 inches, off a bipod.

Has anyone had these kinds of accuracy issues?  I called PRI, and they mentioned that the AE brake could be the issue, and to remove it and reshoot.  Has anyone experienced this?  I don't plan on buying the AE suppressor, but I'd hate to remove the iconic AE brake.

Any advice is welcome, thanks in advance.




-Freq

I'm not sure about the AE brake in particular, but I've certainly have had a muzzle device affect accuracy. It's possible that the change it does to your specific barrel harmonics just puts it in a bad spot.

FWIW:  I have a MK12 with a Douglas Blank, turned by CLE and a CLE chamber.

BH MK262 is a 1.5 MOA load with it.

My hand load MK262, sub MOA, usually .5 - .75.  

I have found that the OAL greatly affected things and the BH MK262 rounds run 2.245-2.250 where my hand loads are 2.260.  Your barrel may not like bullet jump.

Sometimes commercial ammo will hammer in some rifles. Nothing comes close to custom hand loads tuned to your specific rifle. I only have one muzzle break on my AR-15's, it's a Jerry Michulek model on a lightweight build. I personally think it's wasted money, 5.56mm simply doesn't need one.

Standard run-of-the mill A1 or A2 flash hiders work just fine.

I had similar results with mk262 ammo. I switched to 69gr stuff and my accuracy improved dramatically. I could shoot sub moa all day with most groups 1/2 moa.  I only shoot PPU 69gr Match from aimsurplus through my PRI Mk12 Mod 0.

The thing about the AE/Ops system though is it's really intended to have a can on it. The brake I though really was supposed to function as the first blast baffle, no? Otherwise, I'd have zero brakes on anything I own.

Yes, it's essentially the first baffle.  I'd try different ammo, and mine really likes the 69SMK hand loads I actually developed for a .223 bolt gun.

You can certainly try it without the brake, your not hurting anything but I'd try ammo combinations first.

Enjoyed reading this old thread. I just joined this forum and I also have the exact same upper and was experiencing the same accuracy problem. Contact at PRI also said to remove the brake and when I did my handloaded 77 gr Nosler rounds went from 1.5" to 2" to .4" to .7" at 100 yards. PRI offered to exchange the AE brake with one of their in-house brakes. Trade even a $190 brake for a $80 brake? LOL!!! No brake is needed on a 5.56X45 caliber rifle. The shooters next to me like it too.
The test target at 31 yards was one small ragged hole. I wonder if PRI removed the brake to perform that test group?

The whole point of buying a PRI Mk12 upper is, well, the fact that it's a Mk12 upper. Start taking the bits off and it defeats the purpose of buying a Mk12 upper.

Not sure why or how folks are having these problems, certainly haven't seen it with any of my pile of Ops and AE braked and suppressed uppers over the years.

I just had a Centurion Arms MK12ish gun built and I’m getting 1/2 MOA from BH 77gr OTM

I’m surprised it’s not performing better in your PRI.

If you think the muzzle device is the culprit have you considered running a couple test groups without it?

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Good advice has already been shared, but I’ll add my somewhat overlapping two cents. Try different ammo. Sometimes a round will shoot 3/4 MOA from one rifle and 1.5 from another. My PRI MK12 would sing with Hornady steel match 75’s. My Larue barely shoots it better than a higher end 193 load. I would stick with the 77 or 69 SMK though. The 75/68 Hornady projectiles may work great but while they kicked ass in my PRI MK12, every rifle is different.

Also, ensure your barrel is broken in. Some of my best shooters shot like a rack grade AR at first. Seems like it takes maybe 200 rounds for them to hit their stride.

I think that is about normal for every Mk262 I've shot.

Is the AE brake the only muzzle device that is clone correct for PRI Mk12?  I'm not deep enough into any clone corrrct variants for that build.

Did they ever use a different can like perhaps the KAC NT4?  If so, KAC has its M4QD flash hider/mount.  I have one on a Lilja 16" barrel and it does not adversely affect sub 1/2 MOA accuracy,

I do not shoot factory Mk262 ammo, though.  My 77OTM loads are handloads with Berger match bullets.  I do load them out to full mag length.

I agree with posts above that it would make sense to try other similar match ammo before assuming it is the AE brake causing the accuracy issue.