New MK12 MOD O build accuracy issues

[irishbde]

I'm a FNG here and this is my first post.

I just put together a MK12MOD 0 using a PRI upper, and a Noveske lower with Geissele SSA trigger. The the current optic is a Leupold Mark AR 3x-9x 40mm in a Burris Pepr QD mount. Took it to the range for the first time on friday and was somewhat disappointed with the results. From a rest fired at 100 yards I shot a 1" group with 69gr Fed Match, 1.25" with ADI 69 gr match, 2.25 with 55gr PMC, 2.0 with 75 gr Hornady,2.75" with WW 64 gr Lawman SP and 2.25 with 55 gr WW FMJ BT. I expected better and suspect it may be related to the Pepr mount. The PRI upper is fitted with a 1:8" douglas premium barrel.
I'm considering switching to an ARMS QD Ring mount, but am unsure of the appropriate ring height. Any other thoughts or suggestions out there. I've got some IMI 77gr IMI OTM on order. Hoping these will shoot better. e

Thank you

irishbde

 

[RTH1800]

Doubt the mount is the problem. It should shoot better. Who put it together?
Mine are HCS builds. I have shot 3 extensively. Each shoots 5 shots between .5 and .75 MOA at 100 m.
They all seem to shoot better at 600 meters. I shoot various loads, all with 77 grain SMK.

 

[Tangodown911]

Doubt the mount is the problem. It should shoot better. Who put it together?
Mine are HCS builds. I have shot 3 extensively. Each shoots 5 shots between .5 and .75 MOA at 100 m.
They all seem to shoot better at 600 meters. I shoot various loads, all with 77 grain SMK.

I am inclined to agree. I am a fan of the ADM mounts, they have always worked out for me. I would say that you may be able to squeeze a little more from it with the right ammo.

How many rounds through it so far?

 

[irishbde]

I'm gonna say about seventy rounds. Precision Reflex built the upper. I put together the lower. I just feel like it should shoot better with 55 grainers and the 64's. In my experience truly accurate rifles (well built rifles) should not be that finicky. Sure they have a specific load they truly shine with, but they still do fairly well with a variety of loads. I expected well under MOA with Fed 69gr match and the the Outback 69gr. I was also surprised the WW 64 gr lawman and the Hornady 75gr did so poorly. That same day I shot four 168 SMK's with my hand load (42 gr IMR 4895) into a half inch @ 100 yards, with a brand new Rem 700 SPS Tac AAC. I've heard mixed reviews on this gun, but with a couple of modifications I can see a bright future for it.

 

[maggitas]

Mine shoots sub .75 MOA easily. As others have stated the issue is probably elsewhere. Try some different ammo, maybe you had a bad day. What is the torque on the barrel nut? I know HCS recommends the minimum for their builds 35 FT/LBS.

 

[ORD]

Out of curiosity, what did the test target from PRI indicate in terms of accuracy (and it should have the ammo used listed as well)? PRI generally tests their complete upper assemblies/rifles with Black Hills 77gr (Mk262 commercial equivalent) ammo, so you might try to source 50rnds for testing purposes and see what that does for you.

Any way about it, with match quality ammo or reloads tailored to the rifle, you should be able to consistently achieve at least MOA or slightly better performance. PRI guarantees their uppers and complete rifles for MOA (which is generally an "under-guarantee" for what should be obvious reasons), but if you run many kinds of ammo through it and still can't find a "pet load" that gives you at least consistent MOA performance, get in touch with PRI and see what they say. Stuff happens and sometimes you may need to involve the mfg in the process to get the issue resolved. Not saying anything is wrong with your upper at this point, but it is within the realm of possibility.

In the meantime, double-check the torque on your ring cap screws, Burris PEPR mount/base screws and that your scope hasn't @#$% the bed. Similarly, wouldn't be a bad idea to check the torque on the PEQ rail either (both those attaching to the rifle's receiver and those attaching to the handguard). While it certainly wouldn't be the first Leupold Mk AR scope to suffer a FUBAR event (they aren't exactly known for their quality/durability/dependability in the long haul), I suspect it would likely be more mount/ring/etc. related than the optic itself as you still seem to be getting fairly consistent results (albeit not what you want) without wild and unexplainable flyers, etc. As for the ARMS 22 ring option...I'm not a huge fan of their rings, but for "correctness," they do mate up on the MOD0. I wouldn't worry about which height is the "right" height in terms of correctness, but I'd get the one that best fits you to the optic/rifle. I'm betting, with that scope, you could get away with the #22M (Medium) unless you have the OEM ARMS 41 rear sight in which case you may need the #22H for your scope's eyepiece to clear the top of the rear BUIS.

Good luck! Be sure to report back with any findings/updates/etc.

 

[Cobracutter]

Whats the torque settings you used to apply the mount/optic to the upper?

 

[Cobracutter]

Mine shoots sub .75 MOA easily. As others have stated the issue is probably elsewhere. Try some different ammo, maybe you had a bad day. What is the torque on the barrel nut? I know HCS recommends the minimum for their builds 35 FT/LBS.

I dont think PRI sells raw uppers. I assume he means he bought a Mk12 upper from PRI, which means it should already be built to spec.

Possibilities:

Poor Upper Build
Poor/wrong torque settings
Poor Shooter (sounds like the ammo is fine, not too out of wack)


What kind of experince do you have assembling rifles & shooting behind gas guns?

 

[rideHPD]

Try some different match ammo. Mine isn't the biggest fan of the FGMM's (~1") but hammers SWA 77gr SMKs (<.5"). 1" for FGMM doesn't sound out-of-line, it probably just doesn't like it too much.

 

[irishbde]

Thanks guys, I appreciate the valuable suggestions. I spoke with PRI and they are clearly a good bunch of guys. They also suggested checking the rail as well as the ring screws, which I will do. They did test with 77gr OTM @ 40 yards and it put all shots into a single ragged hole. The PRI guy said it should shoot much better with the other ammo I tried and should do better with the 69gr match loads as well. Question: is there a specific torque setting for ring screws? Or did I misread? The ring screws on the Pepr mount were on tight. I tightened up the QD levers and hopefully that will solve the problem.
As for my day. I shot a 1.20" group with my stock M1A and handload and shot a dime sized group with a friend's brand new Rem 700 Tactical AAC SD and my handload. I think I was dialed in that day. (Got to say I'm not crazy about the flimsy stock, but the tube is pretty damn good right out of the box.)

 

[rchman]

I had my PRI forearm come loose, which was hard to notice with the Swan rail. My groups would open up, especially when loading the bipod since it was moving the Swan rail in the slightest amount. May be worth trying to see how it groups without the Swan rail.

 

[J Max]

How much experience do you have shooting semi's? Reason I ask is that I myself had issues with a mk12 after switching from a bolt action, took practice to get right. Also try having one of your buddies shoot it and see what groups he gets. Could try swapping scopes or just remounting yours. Always best to eliminate the small stuff before going to the manufacturer. One other point, those Douglas barrels seem to enjoy the 77 grain rounds more but that doesn't me she can't group nicely with smaller heads.

 

[Scottmilk9]

How much experience do you have shooting semi's? Reason I ask is that I myself had issues with a mk12 after switching from a bolt action, took practice to get right. Also try having one of your buddies shoot it and see what groups he gets. Could try swapping scopes or just remounting yours. Always best to eliminate the small stuff before going to the manufacturer. One other point, those Douglas barrels seem to enjoy the 77 grain rounds more but that doesn't me she can't group nicely with smaller heads.

Shooting a semi is quite different than shooting a bolt gun, plus a 3x9 scope? Nothing wrong with that scope but you really cant expect 1/2" groups with it consistently.

 

[MLC]

Not trying to be a dick here but a lot of the times you see folks unhappy with the accuracy of rifles they just acquired it boils down to lack of experience.
Is this your first AR?

What's the purpose of this rifle you built, shooting tiny hundred yard groups?
You should be looking at a prone or BR bolt rifle not an AR15.

Accuracy is a sum of a rifles parts but applied accuracy has more to do with the driver than the rifle.
From the details missing from your post I don't think you have a lot of experience under your belt.
I would try shooting your rifle at small individual targets at varying ranges and not worry about groups, worry about hits.

 

[BCP]

I'm a FNG here and this is my first post.

I just put together a MK12MOD 0 using a PRI upper, and a Noveske lower with Geissele SSA trigger. The the current optic is a Leupold Mark AR 3x-9x 40mm in a Burris Pepr QD mount. Took it to the range for the first time on friday and was somewhat disappointed with the results. From a rest fired at 100 yards I shot a 1" group with 69gr Fed Match, 1.25" with ADI 69 gr match, 2.25 with 55gr PMC, 2.0 with 75 gr Hornady,2.75" with WW 64 gr Lawman SP and 2.25 with 55 gr WW FMJ BT. I expected better and suspect it may be related to the Pepr mount. The PRI upper is fitted with a 1:8" douglas premium barrel.
I'm considering switching to an ARMS QD Ring mount, but am unsure of the appropriate ring height. Any other thoughts or suggestions out there. I've got some IMI 77gr IMI OTM on order. Hoping these will shoot better. e

Thank you

irishbde

That sounds like it is working fine to me you just need to figure out what it likes.

Your mount and that leupold optic aren't doing you any favors, I had zero retention problems with that burris mount and parallax issues with the leupold Mark AR. Get something with higher magnification and a parallax focus as well as torqued rings if you really care about your group size.

The ARMS 22MH (1.15") are the rings you want with the SPR upper if you have the SPR top rail/swan sleeve. You will be able to use up to a 50MM objective with them but it will be really really tight.

***also, with the SPR rail a regular QD mount will be about .4" too high for your eyeball. That will hurt you accuracy wise as well.

 

[Cobracutter]

The ONLY reason to go with ARMS anything, is for an exact clone. Their products are absolute garbage, and if you value your optics, stay away (unless doing a close as stated)

AMU should have had their dicks stomped on for using their products on this gun. They should have used a solid mount with supplied torque wrenches. Yes ARMS was one of the only games in town at the time, but they still stucked.

 

[eodcam]

Is your gas block pinned or set screw? If it is set screw check if its tight.