AR build, shooting low and left, how to fix?

T

TexasCop

New member
Okay, briefly, have a dissipator style barrel that used to be on an A2 upper, it was shooting low and left (extremely)

I took that upper assembly apart and remounted the barrel onto an A1 upper, it is STILL shooting low and left, so much that I have the front sight dialed all the way down and the rear sight all the way over to the right and it's STILL not shooting straight.

Any ideas on what I can do to fix the problem? How do you bring the barrel into alingment when everything is constant?

Oh, pinned A2 front sight, so it's not a set screw system that could be off or anything.
 
Is it possible that the handguard or someother part is putting pressure on the barrel? This could throw it off with the backsight.
 
in agreement that the barrel could be bent. Don't think that the handguards cold be putting enough pressure on the barrel to cause it to shoot that bad, but you never know. If the barrel shot the same after being installed on 2 different uppers than I am thinking it is the barrel.
 
The front sight base is mounted crooked, there is nothing you can do to fix it without removing it and mounting it straight. If it isn't way out you can line it up and ream for taper pins, then pin it back on. The easy way to fix it is to ditch the pins to put an adjustable front sight base.

If it is so far out you can't adjust the sights you should be able to see that it is crooked with your eyes.
 
"The front sight base is mounted crooked, there is nothing you can do to fix it without removing it and mounting it straight. If it isn't way out you can line it up and ream for taper pins, then pin it back on. The easy way to fix it is to ditch the pins to put an adjustable front sight base.

If it is so far out you can't adjust the sights you should be able to see that it is crooked with your eyes."

I agree with the above. Can't think of anything else it would be.
 
The front sight base isn't crooked, and I don't think the barrel is bent from what I can judge here. I've looked at the brake on the end and it looks like there might be a slight brass deposit on the upper right part of the hole the bullet comes out of, I'm wondering if maybe the bullets are "skipping" off this and going low/left after the impact.

I'm going to try taking the brake off and see if that makes the rifle shoot straight.
 
I guess the muzzle could have been grossly misthreaded, but a crooked or misaligned front sight (the pin groves could have been cut incorrectly) would be most likely.
 
The flashhider could DEFINATELY cause the problem too, but is very rarely the cause. Take it off and see where the POI goes, if it is better/good all you need to do is have it bored out where it won't be hit by the bullets or have another one fit correctly. If it doesn't fix it the front sight base is most likely. I don't recall a problem like yours where the FSB wasn't the problem, but I have seen exactly what you are having from bullets hitting muzzle brakes or comps. If the bullet is hitting the FH/Comp/brake accuracy is going to be terrible though, does your gun actually group decently?
 
thr gun groups well, that's my one problem with thinking it's the muzzle brake, I would assume that the impact, no matter how slight, would make the grouping suck, but the groups are in line with what I normally shoot out of an AR, but I took the brake off last night and I'm going to take it to the range this week (hopefully)
 
If it's an aftermarket brake, that could be it. Aftermarket brakes usually have LOTS of bullet clearance tho. Let us know how she does.
 
If it grouped well and there were no bullet marks on the comp it sounds tremendously like the Miculek comp wasn't clocked right. I would put it back on and try clocking it to see if the POI will come in. They generate tremendous forces on firing and can easily move the gun.
 
I don't know whether it was a bad comp or if the gun was not threaded right, the A2 has a much bigger area for the bullets to pass through. With the comp off I can see just a bit of copper fouling on the top right of the last hole so it definately looks like the bullets were hitting and "bouncing" to the low left.
 
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