AR 15 Shooting Left

[Tenko]

Hi there,

I picked up a new AR 15 from a local shop. Store owner said it was a custom build done by a certified gunsmith. It is a Spikes Tactical ST-15 receiver set with a Spikes BCG, POF charging handle and stock, bcm trigger, as well as a 15" Fortis night rail and muzzle break.

I took it out to the range, was shooting PMC 5.56 at 25 yards. Shots all grouped about 4" left. Thought it may be me, so I used a block to eliminate as much of me as possible. Half inch group 4" left. I thought it may be the UTG sights I put on it, so took the Magpul flip ups off another rifle and tried it again, same thing. To correct the issue, the sights have to be pretty much maxed to the right. I visually expected the alignment between the barrel and the rail, and it appeared to be about a tenth of an inch to the left. Im not sure if this is an issue of an incorrectly installed rail, or barrel, but I want to get it corrected. I would rather not just adjust the sights, as I would like it to be mechanically zeroed. The rail feels secured, and the barrel does as well, although the barrel does flex (I'm relatively new to the AR platform but I believe this is normal).

Any help on what to do would be greatly appreciated!

[bamboomaster]

Many rear sights can be adjusted even when mounted.

Move the rear sight in the direction you want to go - in your case, move the rear sight a tad to the right, then fire a three shot group. Further adjustments, a little more to the right or a touch back to the left will depend on the impact of your three shot group.

Hope this helps.

[unclejumbo]

Define flex.

You could have a loose or misthreaded barrel nut. You could also have a bent/warped barrel.

[Tenko]

@unclejumbo Basically, when I grab the barrel and pull it in any direction, it moves in that direction. It seems to return to its original position, although I am not 100% sure. How would I know if I had a bent barrel? Is there a way I can test that?

@bamboomaster What do you mean adjust it while mounted? As in adjust for windage? If thats what you mean, I did that, but nearly maxed the windage on my sights and I would prefer to mechanically zero.

[unclejumbo]

@unclejumbo Basically, when I grab the barrel and pull it in any direction, it moves in that direction. It seems to return to its original position, although I am not 100% sure. How would I know if I had a bent barrel? Is there a way I can test that?

@bamboomaster What do you mean adjust it while mounted? As in adjust for windage? If thats what you mean, I did that, but nearly maxed the windage on my sights and I would prefer to mechanically zero.

If your barrel is moving, it sounds like your barrel nut is loose. You won't get flex in a barrel by simply grabbing it and moving it. Easy fix if you speak AR.

[marinville]

I would believe that the rail is flexing, but I doubt the barrel is. An AR15 barrel extention fits pretty snugly into the upper receiver, even with the barrel nut loose.

If by mechanically zeroed you mean zero clicks of windage from center, that just isn't realistic.

[Tenko]

@unclejumbo If thats the case, then thats alright by me. Ill bring it by the shop I got it from and have him tighten it up as I don't have the proper correct tool. You did say something about having a bent/warped barrel. I know this is probably not the case, but is there a way I can check just to make sure?

@marinville The rail I believe probably has a bit of play. I will try to tighten it a bit more. Is there a way to make sure the rail and the upper receiver are properly aligned? Also, that is what I meant by mechanically zeroed. I know its not going to be perfect, but I just have to believe it can be better than maxed to the right.

[unclejumbo]

@unclejumbo If thats the case, then thats alright by me. Ill bring it by the shop I got it from and have him tighten it up as I don't have the proper correct tool. You did say something about having a bent/warped barrel. I know this is probably not the case, but is there a way I can check just to make sure?

@marinville The rail I believe probably has a bit of play. I will try to tighten it a bit more. Is there a way to make sure the rail and the upper receiver are properly aligned? Also, that is what I meant by mechanically zeroed. I know its not going to be perfect, but I just have to believe it can be better than maxed to the right.

I suppose it would depend on how much bend there is. I'm sure a smith can check it. Rolling the barrel like a pool cue on a flat surface should reveal a bend. Looking down the barrel if it's pronounced enough.

[Tenko]

It isn't noticeable by eye. I'll probably end up bringing it back to the shop so he can contact the smith that built it. I won't be able to make it over there until thursday/friday though. Hopefully something is just loose and can be fixed on the spot. I will keep this thread updated. Thank you for all your help sir!

[pennlineman]

Loose barrels usually don't group well. For a warped or bent barrel they do make barrel straightness gauges but this is rare. Sometimes there is some slop between the receiver notch and barrel extension locater pin. An indication of this would be a canted barrel. If you're hitting left the front sight canted to the right would cause this. In my opinion this is a problem for the gun shop owner and/or "custom builder." Make it right or a refund IMO.