AR accuracy problems

[hunterdan]

I took my AR out today for the second time, and was trying to sight it in using a redfield 3-9 scope. The first outing, the scope mounts were too low and I couldn't get a good, comfortable cheek weld. I've since changed the rings for higher ones that feel much better. Torqued everything down and went out today. The scope mounts are all on the receiver, not bridging the rail at all. Started off at 25 yards and was just a few inches low and right. 5 shot groups were a bit large for that range, but it grouped. Made a quick minor adjustment to the scope, and moved back to 50 yards. At this point my groups really opened up and couldn't get any consistency. I was shooting off a bipod, but took it off and moved to sandbags. Same result. My groups at 50 yards are probably 6-7" wide and very erratic. I'm not expecting pin point accuracy, but I don't think it's unrealistic to expect about 1-1.5 moa. I'm using federal AE 5.56 55 grain. I haven't tried any other ammo yet, but I find it hard to believe that to be my culprit. My setup is an Anderson lower, mil-spec lower parts with PSA full auto bcg and charging handle, and CBC upper with free float Hera arms quad rail.
http://www.sportsmansguide.com/produ...rail?a=1879510
That is the upper I have.

That was my final 5 shot string at 50 yards. I was aiming dead center of the target, between the 4 dots.

That is my current setup, except the scope was moved back so both mounts were on the receiver.
Any ideas on what to look for it check? I'm not a sniper by any means, but I'm capable of shooting 1 moa or a little better with my 17 HMR and .30-06 bolt guns. Any tips would be appreciated. I'm a little disappointed, being my first build, I expected better results.

[McSull]

first thing I would look at the scope and mount, make sure everything is tight. your also on the handguard, is there any play in the handguard. I always mount to the receiver.

[hunterdan]

first thing I would look at the scope and mount, make sure everything is tight. your also on the handguard, is there any play in the handguard. I always mount to the receiver.

I moved the scope mount back off the handguard before my range trip after another member mentioned it in a post a few weeks ago. The handguard is tight, and the scope and rings are all tight.

[McSull]

I like to use process of elimination. I would try a different scope next. I own ARs, but I'm by no means an expert.

[edritchey]

Pull the flash hider off the barrel and look at the crown on the muzzle of the barrel if it looks good try another scope. If you built the rifle what did you torque the barrel nut to? How much play is there between the upper and lower fit? That is a shitty group you could probably throw stones that accurate.

[hunterdan]

Scope was pulled off of my .30-06 a few months ago, and I had zero issues with it. It was sitting in the box my new scope came in, on a shelf in my closet. I have another scope I can swap on though to test that theory out.

[hunterdan]

Pull the flash hider off the barrel and look at the crown on the muzzle of the barrel if it looks good try another scope. If you built the rifle what did you torque the barrel nut to? How much play is there between the upper and lower fit? That is a shitty group you could probably throw stones that accurate.

I bought an assembled upper, so I'm not sure what the barrel was torqued to. I'll try to remove the flash hider and inspect the muzzle.

[Bang]

I think the barrel is wobbling in its seat. This happens now and then...defective machining of one of the surfaces or the locating notch. Contact the manufacturer or ask the dealer to take it back and give you another one...if you bought it new. If bought used, you have found out why it was for sale.

[edritchey]

If the crown looks good I'd check the torque of the barrel nut I've bought complete uppers that were only hand tight it's not that uncommon and will toss the shots all around if it's loose.

[Bang]

On looking at the target, I think I see signs of yawing projectile. Try 62 grain ammo.