AR 15 Accuracy & upper/lower fit

[Flynt]

I'm trying to mate a RRA 5.56 uppper (16.25" 1:9 barrel, free floating hand guard) with a Bushmaster lower. I'm getting poor groups, 2-4 inches @ 100 yds. depending on make of ammo. I notice that there is some play in the mating of the the upper and lower. I can hold one in one hand and the other in the other hand and twist -- and feel a tiny bit of rotation. Could this affect accuracy? Thanks.

 

[snakeman]

usually this does not affect accuracy much. If there is enough play it can open up groups. Look into an accuwedge. also, look for other sources of inaccuracy such as, bore, crown, hanguards, operator error etc.

 

[kcshooter]

That doesn't have a significant effect on accuracy. The sight/scope are on the same part of the gun as the barrel, so it stays true regardless. It can affect cheekweld, and therefore eye placement, but you've got to get pretty loose before that happens.

 

[mljdeckard]

Not usually. What kinds of ammo?

 

[Infidel4life11]

Flynt: how are you shooting, from a bench, prone with, without sandbags, standing crouched?

 

[Flynt]

I actually got one .75" group with an old box of Black Hills 55 gr. FMJ. I only had six rounds, so I saved the remaining three to verify results.

With the following ammo I got 2" groups:
Remington Premier 55 gr. Accu Tip (ballistic tip)= 2"
Federal Bulk 55 gr. FMJ = 2"

With the following ammo the groups were so bad I didn't record the info:
Winchester White Box high velocity varmint 45 gr. JHP
XM193F 5.56M 193 Ball 55 gr.
Remington 45 gr. JHP
Black Hills 68 gr. Heavy Match HP

I'm shooting from a bench with sandbags, using 2-7 Leupold scope and burris AR mount. Thanks.

 

[JustinJ]

2-4" is not uncommon with xm193(bulk 55 grain federal). You can try an accuwedge. I've read they can improve accuracy by 30% but doubt they can help nearly that much.

I actually got one .75" group with an old box of Black Hills 55 gr. FMJ.

How many rounds per group? One good 3 shot group tells one very little about a rifles's accuracy.

 

[Flynt]

Justin, it was a three round group. I understand that could have been a fluke. I'll try the remaining 3 when I go back to the range. Even if I get good results, I'm not sure how much that helps me. The box was 10-12 years old. Not sure Black Hills still makes that load.

 

[cfullgraf]

55 FMJBT bullets are not the most accurate bullets in the box.

Try some quality bullets with an open tip or polymer tip, basically a closed base bullet. Match or varmint types.

I feel something to tighten the fit between the upper and lower frame is beneficial. Te Accu-wedge is one way. There is a locking pin offered by another vendor, JP Enteprises I think.

While in theory, the sights, barrel, and chamber are locked together in the upper, some looseness in the fit between the upper and lower could cause a flier. Yes, the bullet went where the barrel was pointed but the looseness allowed the barrel to move slightly at the moment of let off.

Accu-wedges are cheap to try and easy to remove it does not help.

 

[Flynt]

cfullgraf,

Good advice about the bullets. Regarding the accuwedge, that makes sense as well. I have a Marlin 1894P, which was making one hole groups at fifty yards. I tinkered with her a little and failed to tighten the screw that secures the butt stock. My shots were all over the place until I realized I had a screw loose (literally). Tightened butt stock & frixed problem.

 

[TonyAngel]

The slop between the upper and lower have NO effect on the accuracy of the rifle. The Accuwedge is a gimmick product and does nothing for you. If it makes you feel better to tighten up the fit, put a rubber o-ring around the front lug of the upper receiver. It will tighten up the fit.

Assuming that you are an accomplished shooter with an AR (which are harder to shoot well than a bolt gun), get a box of 69gr Federal Gold Medal Match and see how it does.

 

[Infidel4life11]

The slop between the upper and lower have NO effect on the accuracy of the rifle. The Accuwedge is a gimmick product and does nothing for you. If it makes you feel better to tighten up the fit, put a rubber o-ring around the front lug of the upper receiver. It will tighten up the fit.

Assuming that you are an accomplished shooter with an AR (which are harder to shoot well than a bolt gun), get a box of 69gr Federal Gold Medal Match and see how it does.

agreed

 

[Warp]

Why only 3 round groups? Plenty of room for luck or coincidence with only 3 shots, seems to me.

Don't believe the marketing put out with the accuwedge. As mentioned above, the parts that matter are all on the upper. Barrel, front site, rear site, any optic, etc. Cheek weld was mentioned, yes, but shooting for groups nice and slow on the bench...shouldn't make any difference far as I can see.

 

[velocette]

Tony Angel has it right.
Get yourself some good ammo and try it. The Federal GMM with the 69 gr Sierra match bullet (Hollow Point Boat Tail Match) is a great start.
Cheap FMJ ammo usually yields a 2 ~ 4" group @ 100 yds.
Try reloading using the Sierra HPBT M bullets.

Roger

 

[Slamfire]

The slop between the upper and lower have NO effect on the accuracy of the rifle. The Accuwedge is a gimmick product and does nothing for you. If it makes you feel better to tighten up the fit, put a rubber o-ring around the front lug of the upper receiver. It will tighten up the fit.

Bing, Bing, Bing! We have a winner!

One shooting bud of mine was recognised by the NRA as one of the best 200 shooters in the US. We were discussing AR tightness and accuracy and he pointed out that you could take his lower and just move it in an arc around the upper.

Tightness does not make a difference in accuracy in these things. I like my space gun to be tight, but that is just a preference.