My newly acquired Bushy (purchased used) seems to be somewhat loose between the upper and lower.  The upper can kinda rattle around a bit.  Is this normal, and does it have an adverse effect on accuracy?  I vaguely remember reading about some kind of product that was designed to "fix" this.

--Mike

A little movement is pretty common on used AR's.  If you place a loaded magazine into the well, the upper should tighten right up.  If it's still sloppy or if there's a problem charging the rifle, then you may have a problem, but the magazine always took the slop out of my M16A2 while I was in the service.

Normal.  Some rifles are tighter than others.  Arguments on accuracy are all excercises in theory.... and are not much of an issue for an M4, since that is not set up to be a varmint/benchrest gun in the first place.

If it really bugs you, buy an accuwedge.

A little wiggle is not big deal, but if it bugs you too much, accurwedge is the way to go.

Armalite also reportedly sells oversized push pins that they put on their National Match rifles and theoretically, they could help, though I believe you need a punch to drive them out (can't be pushed out by hand).

The only accuracy problem you should have is in actually keeping a point of aim if it's really sloppy, as you are keeping your cheek on the lower and if the upper moves just a small amount, your shot could be off a bit.  The inherent accuracy of the upper itself, however, should be unaffected, just the entire upper's movement on your target.

A bit different compared to a pistol where the "upper" (slide) being too sloppy can theoretically affect accuracy.

Try it out at the range first.  If it gives you trouble there, then try one of the aftermarket solutions.

Thanks, I'll try her out at the range this weekend (hopefully) and see if it's a problem.

--Mike

I bought an upper from Bushy and the fit was loose so I sent it back along with my lower and asked for one that fit tight. Two weeks later I got back one that fit a little tighter, but I still bought an accuwedge and a pair of Armalite NM oversized pins. I noticed that the pivot pin was too small for the hole so it was allowing some wiggling. The rear take down pin fits better. As for the accuwedge, it pushes the rear part of the upper slightly higher so I think it affects the action of the bolt a little. However it does make the fit tighter. I haven't gotten the oversized pins yet, which are suppose to be .002 larger than standard pins. You could also buy a the tension pin, but they cost alot and needs a tool to take down.

Try the Accu-Wedge. It's the only good use for it, firming the fit of a worn/loose fitting upper/lower.

Less than $5.