BCM AR Accuracy Woes Caused By Muzzle Brake ?

Jackal · Apr 28, 2014

So, I purchased a nice BCM 16" midlength lightweight .625 complete upper. Immediately upon receiving it, I installed a Ranier Arms XTC brake. I now have about 200rds through it and I have never been able to achieve anything better than about 3moa from it using a 9x optic. I have tried several loads, all in the 50gr to 62gr region (mostly 55's and 62's). I have noticed a large amount of exposed threads within the muzzle brake, which I am concerned is affecting the projectiles accuracy. Its installed correctly. Has anyone else seen this many exposed threads inside their muzzle device?? If so, did you notice any affects on accuracy? It really seems that I should be able to do better than 3moa with a new BCM....:banghead: , when my PSA with 16" FN pencil will nail 1moa groups with fair regularity.

wally · Apr 28, 2014

Looks like you have both a crush washer and a peel washer on it, using only one would reduced the exposed threads, but from the photos, not eliminate them.

Before doing anything rash, remove the muzzle device and just try the plain barrel.

Jackal · Apr 28, 2014

Looks like you have both a crush washer and a peel washer on it,

It is indeed just a single crush washer, just has a small bevel on it.

NCsmitty · Apr 28, 2014

As mentioned, have you tried it without the brake? Milspec FMJ ammo is notoriously inaccurate compared to spitzer & HP ammo.

NCsmitty

Jackal · Apr 28, 2014

I have not yet tried it without the brake. I have been shooting Wolf Gold fmj 55gr, Federal fmjbt 55gr, fed 62gr green tip, federal ae 50gr hp's, Rem 55's, etc. Does a standard A2 style flash hider have exposed threads inside too?

mtrmn · Apr 29, 2014

Don't know about the threads, but many of the different ammo types you named off are not known for accuracy. If you suspect the muzzle device then take it off and try it with bare muzzle like others suggested.
In all my years of tinkering with these things, I have consistently found that each gun prefers a certain brand/type of ammo in order to be accurate. And finding that ammo makes by far the biggest improvement unless you have mechanical problems like loose scope mounts etc. Not necessarily expensive ammo, but consistent and loaded to a pressure/velocity that agrees with the harmonics of that particular barrel. I reload, so I can develop pretty much any load I want provided I can get my hands on components.

browningguy · Apr 29, 2014

As already mentioned try it without the brake (and I've never seen that many exposed threads), and get some decent quality ammo to run through it. Black Hills reloads in 52 gr. Match HP or their 69 gr. stuff. If it won't shoot those then you can say there is something wrong with the upper.

C-grunt · Apr 30, 2014

What is the setup of the upper? Is it free floated or a standard type with the slip ring and front cap?

Jackal · May 2, 2014

What is the setup of the upper? Is it free floated or a standard type with the slip ring and front cap?

Standard with MOE handguard and A2 front sight. Today I installed a A2 flash hider, I'll test it out tomorrow afternoon with the same ammo/optics. It will be interesting to see if the muzzle device has a significant impact on accuracy.

orphanedcowboy · May 2, 2014

I pulled the threads using a crush washer on a 1/2-28 threaded barrel once, never use them now. I use low strength loctite and a peel washer. I had to have the barrel cut and crowned to fix it. According to Harrison Beene, there are crush washers that are over hardened and cause problems.

Jason248 · May 2, 2014

Mine has about 1/4" threads showing on my XTC. I just have two of the spikes shims in there to clock it and no crush washer. I can only shoot out to 200 in town but it does shoot moa

GooseGestapo · May 2, 2014

I had a Bushmaster 16" Carbine with .625" bbl.
As "issue" with std handguard, with similar ammo to yours it was also a 3moa rifle.

I installed a free-float handguard and YHM gas block and a DPMS hi-pro "slick" reicever. It would then shoot a 55gr Nosler BT or Sierra 55gr Varminter into ~1/2"@ 100yds.

So, I say it's a combination of rifle and ammo......Not the muzzle brake.

George44 · May 2, 2014

It sounds like your using mil.spec ammo which is about 3 MOA ammo.

BCM AR Accuracy Woes Caused By Muzzle Brake ?

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