AR15 Shooting Right

[Dragline45]

I haven't shot this rifle much, but I noticed it is hitting right and I need to adjust the rear sight to the left more than I should to compensate. The upper itself is a BCM, and the sights are Troy Folding Battle Sights which are legit and bought through Primary Arms. My worst suspicions are that the gunsmith who installed my muzzle brake maybe did so improperly and messed something up. I never shot the rifle before the muzzle brake was installed so I have nothing to compare it to. Short of pulling the barrel off which I don't feel comfortable doing myself, is there any way to check to see what could be the culprit? If damage was done from installing the muzzle brake what should I be looking for.

[ed308]

Most likely the upper receiver needs to be lapped. I lap all my uppers in a build for the same problem you're having. Takes 5 mins.

https://www.youtube.com/watch?v=7uMtxvdZ0HM

[Dragline45]

Most likely the upper receiver needs to be lapped. I lap all my uppers in a build for the same problem you're having. Takes 5 mins.

I'd expect a high quality upper like BCM who have strict quality control to either not need to have that done or already have it done.

From what I can see the gas block doesn't look like it has moved nor does the feed ramp look off. I've read online that an improperly attached muzzle device if not secured at the barrel or over torqued could shear the barrel index pin and throw off the alignment. Again not sure if there is any way to tell if this has happened other than pulling the barrel off.

[ed308]

I'd expect a high quality upper like BCM who have strict quality control to either not need to have that done or already have it done.

Expensive or inexpensive you never know until you build it and get results. Some uppers don't need to be lapped. But most benefit from being lapped for the exact problem your having. That's why I lap every upper I built. Takes 5 mins with the Wheeler kit I use. I've lapped older uppers which had the exact same problem you're having. And every time that fixed the problem. With that said, the muzzle device would be the second area to investigate. You could always remove the muzzle device and see if that changes the impact point. Certainly easier than removing the barrels.

[TnTnTn]

How is the front sight mounted? Gas block or top rail-make sure the front sight is not canted on its mounting platform. A little cant on a tall sight throws the shots a long way off.

[Mobuck]

" Some uppers don't need to be lapped. But most benefit from being lapped for the exact problem your having. That's why I lap every upper I built."

I'm not sure why "lapping" an upper would change the POI but if it makes you feel good, have your fun.
For the OP, It's quite possible to twist the barrel in the upper w/o shearing the alignment pin. If the "gunsmith(?)" used an upper receiver block rather than securely clamping the barrel during the muzzle brake installation, this oops is quite possible.
On the other hand, a clamp on sight is very likely to have some "tolerances" which could cause sight alignment problems so here's my suggestion. Center the rear sight and use a laser bore sighter to compare bore line with sight line while looking for anomalies/mis-alignment of sight, receiver, rail, and any other points of interface.

[ed308]

I'm not sure why "lapping" an upper would change the POI but if it makes you feel good, have your fun.

I don't do it because it makes me feel good. I do it because it's worth the extra time so you won't have the same problem the OP is experiencing. Lapping trues upper receivers to ensure a precise fit between the barrel nut and the upper receiver. Barrels don't always sit flat in the upper receiver due to unevenness of the metal or coatings. And if not sitting flat, the barrel won't be pointing straight but will be canted to the left, right, up or down. So when you lap, the POI moves as the angle of the barrel changes. The best way to tell if a upper needs to be lapped is to lap it. If the material comes off uneven as you lap the upper, then it needed to be lapped.

I've built over 15 ARs. Of those I've built, I've only seen one or two that didn't benefit from being lapped. Case in point, my oldest AR was assembled back in the early 1990's. The rear sight was always canted almost all the way to the left. After I lapped it, the rear sight was almost perfectly aligned. Maybe one click to the left. It's worth the time to lap.