AR10 Accuracy with folding butt question??

[swd]

I normally don't work on these things, but I had a client bring one with accuracy problems and I got suckered into it. I confirmed it's shooting around 3"-5" at 75 yards. This thing has a telescoping butt stock like so many tacticool rifles and in any position the back half is loosey goosey as can be. Seems to me this would act just like bad bedding? The groups seem mostly but not all vertical. What's the thoughts on these things? I don't want to be digging a lot deeper if this is an obvious problem.

 

[mac86951]

Sights are on the upper with barrel. Back half being loose goosey can cause consistency troubles you are correct, but big accuracy problems not so sure, good bench practice should negate some of that.

Try a straight A2 stock, buffer tube and full size buffer. That'll let you know for sure. (Choate makes an A2 type with butt hook and rides bag ok, otherwise EGW bag rider).

Big accuracy problems, something is loose. Is barrel free floated, is barrel nut tight, is gas tube mis-aligned, etc...

Also, what ammo are you trying? What caliber is it, if 308; typically they should be 1" or better with FGMM 168gr at 100y, otherwise something is awry.

I'd look to loose barrel nut, or non-free floated barrel first, ammo second, buttstock is a longer shot, but worth a disassemble and reassemble to ensure the right parts are in it.

Just my experience, keep us posted.
-Mac

 

[jonbearman]

Does the lower have play with the upper,(pin fit) can cause a lot of problems. I have one with an std A2 stock, no free floated barrel and off bags with my match loads using a 168 grain hornady bullet with blc-2 powder,scoped it will shoot under a half inch until it gets warm. Then I let it cool after 5 rounds. Continuous fire will play havoc on any rifle and the AR-10 is no different. Look at the bulged end of the gas tube to see if there is wear on it. If so then the other poster may be on to something. Is it an armalite or dpms or something else? How coppered is the barrel, maybe the guy didn't know how to clean it in regards to copper. If the rifle is new, then he should call the company and send it back to them for testing and disassembly, cleaning with careful reassembly.

 

[swd]

It's a Black Rain. The upper and lower have about .003"-.005" clearance. I shimmed it to take out all the slop. I'll dive into it and take a look at everything. I need to swap out the scope for one of mine too. The $150 POS just might be the problem. It amazes me how a guy will spend $1500-$2K on a rifle and then buy a scope that's no more than the sales tax on the rifle.

 

[Zero333]

I put a telescopic butt and pistol grip on my mossberg 535 12g. With the rifled barrel and Hornady sst sabbots it shoots 2" at 110 yards. with 1x red dot sight too. Recoil is heavy since the buttstock doesn't have a recoil pad, just a very thin piece of rubber to stop it from slipping on the shoulder.

So I don't think the telescopic stock is the main problem with the rifle you're working on.