New AR build keyholing

[Weg]

Anyone ever have a brand new AR barrel Keyhole right out the box? Just built and new AR with a DMPS barrel (maybe that's the problem) that keyholes at 50 yards with both 55 grain and 62 grain loads. I guess I'm pulling it and putting a FN on it, never had problem with those.

[Mike S]

Silly question, but have you looked to make sure the barrel has rifling?? That would be crazy, but it IS 2020...

[jason812]

Only rifle I have ever seen keyhole was shooting a .270 in a .30-06. Check the bore diameter.

[grim-bob]

What is the twist rate? Most should stabilize 55gr but not always. Certainly worth checking the crown after pulling the flash hider and maybe shooting without it to remove one more variable. DPMS barrels should be perfectly fine. They aren't bottom bin or anything....

[bobby]

as stated check bore for rifling also check the markings on the barrel. Even DPMS barrels shouldnt keyhole.

[Paladin]

I've shot a lot of AR's and the only one that ever keyholded was an M16 with a shot-out barrel.

[Jusme]

I agree with other posters. Sounds like a barrel issue. Check bore diameter, and make sure they didn’t mis-label a 300 black out barrel. Or maybe rifling way off, or non-existent. With demand at an all time high QC may not be as stringent as it should be. JMHO

[The Annoyed Man]

Have you tried firing other brands of ammo through it? Sometimes poorly manufactured ammo will keyhole out of a perfectly fine rifle that shoots other loads just fine.

[Weg]

Thanks for all the feedback : it's a 1 in 9 twist, I have tried 2 different kinds of ammo in it, 55 grain reloads, and 62 grain S. African Ball which shoots great in all my other AR's. The crown looks good, and the barrel bore is 5.56. One major thing I omitted is that I am test firing it with a direct thread .30 caliber suppressor, which I use on all my other Ar's. I've checked it real well for baffle strikes, and I don't see any, but i'm beginning to think the suppressor is somehow playing into this. I'll have to wait a few weeks to test fire it at a location that I can shoot it without the suppressor, gotta keep the peace with the neighbors, but I will report back once I do that. Thanks

[The Annoyed Man]

Thanks for all the feedback : it's a 1 in 9 twist, I have tried 2 different kinds of ammo in it, 55 grain reloads, and 62 grain S. African Ball which shoots great in all my other AR's. The crown looks good, and the barrel bore is 5.56. One major thing I omitted is that I am test firing it with a direct thread .30 caliber suppressor, which I use on all my other Ar's. I've checked it real well for baffle strikes, and I don't see any, but i'm beginning to think the suppressor is somehow playing into this. I'll have to wait a few weeks to test fire it at a location that I can shoot it without the suppressor, gotta keep the peace with the neighbors, but I will report back once I do that. Thanks

Suppressors can be hit or miss when it comes to their effect on accuracy. (See what I did there?)

Humor aside, that’s absolutely true. Also, have you checked to see if the can loosened even a little bit while shooting? That could have a profound effect.

FYI, all other things being equal, 1:9 and 1:8 twist barrels will be slightly more accurate than a 1:7 barrel, using 55 and 62 grain bullets.

[bobby]

Yep The Can I bet. Baffle strikes are not needed to upset a bullets flight. Make sure can is tight Fire 3 rounds check for keyholing if keyholing then take off can put a shim on and reapply the can. Test fire again. try this 3 or 4 times to see if it stops

[The Annoyed Man]

Yep The Can I bet. Baffle strikes are not needed to upset a bullets flight. Make sure can is tight Fire 3 rounds check for keyholing if keyholing then take off can put a shim on and reapply the can. Test fire again. try this 3 or 4 times to see if it stops

Also, there’s a way to check if the barrel threads are concentric to the bore (I have one rifle on which they are not), and that’s with a bore alignment rod: https://www.surefire.com/products/suppr ... ment-rods/.

Insert the rod into your bore at the muzzle end. Attach the suppressor by passing the bore of the can over the rod and then threading the can onto the muzzle. The tip of the rod protruding past the end of the suppressor will show you if the threads—and therefore the suppressor—are concentric to the bore. The OD of the end that goes into the muzzle is exactly the ID of the lands of the rifling inside the muzzle. The OD of the portion that protrudes from the barrel is exactly the caliber dimension. So the one I have for my .308 rifles is .308” at the end that protrudes from the endcap of the suppressor, and very slightly smaller than that at the end that inserts into the muzzle. This is what made it impossible for me ultimately to continue trying to suppress my Ruger Gunsight Scout. The misalignment didn’t hurt my AAC 762-SDN-6, but it caused a pretty severe baffle/endcap strike on my Form 1 can which is about 2.5” longer. And even before the baffle strike, it really threw off the rifle's inherent accuracy.

[Weg]

Thanks TAM! Never heard of such a thing, but I just ordered one, and will report back with what I find when it gets in.