Play between lower and handguard

[DennisR]

Hi guys,

I have an off the shelf 450BM from Bushmaster with the 20" barrel and A2 stock. I noticed that, if I hold the stock in one hand and the handguard in the other and twist, there is a small amount of play. It isn't from the stock, because I notice the same thing if I grab the lower receiver itself instead of the stock. Is that normal? I am thinking it isn't, but I don't know for sure.

I did also grab the barrel itself with one hand and the lower receiver with the other and twisted, and I don't notice the play then. But it is a little harder to get leverage that way also. I don't have one of those large front sight bases to grab.

Does this sound like a loose barrel nut?

Thanks,
Dennis

[Jim in Houston]

I had this problem on my 5.56 AR, and I think "looseness" between the upper and lower is a common observation. If your barrel nut were loose, I think you would also observe movement between the barrel and the upper.

Here is a YouTube video on one solution - https://www.youtube.com/watch?v=We4iLuvkVB0.

I used an AccuWedge on mine - https://www.youtube.com/watch?v=6NoL6NrNRBM - http://www.midwayusa.com/product/518277/utg-accurizing-wedge-ar-15

[plant_one]

the play between and upper and a lower shouldnt effect anything - including accuracy.

as long as the upper is properly assembled and theres no play between the barrel and the upper receiver you should be just fine.


i have some upper/lowers that are tighter than a fishes butthole, and others that are rattletraps and i dont see any significant difference in accuracy between them - they all can perform sub MOA.

[commander faschisto]

That's probably from the "plus-or-minus" manufacturing tolerances interacting with your upper and lower. Did you turn it upside-down, with the pistol grip up, and try the twisting motion while looking at the front takedown lug and ears? Pull front-to-back also and check for movement. If there is some there, its really nothing unusual on the AR, but if it bugs you, you might try installing an oversized front pin, which can be had from several sources.

[DennisR]

Thanks. I'll take a closer look tonight to be sure the play is between the upper and lower. As long as it is ok, I am fine with it. I just didn't want to overlook something that might be wrong. When I was reading the cleaning manual for the gun, it mentioned twisting the gun to check if the barrel nut was tight, so that is what got me concerned.

[DennisR]

I separated the upper from the lower and checked for play. You were right, the play is definitely between the upper and lower. So it isn't anything I need to worry about. Thanks for the help.

[BayShoreBallistics]

The play between upper and lower receiver doesn't mean much to accuracy but it does to my confidence. For that reason I would install an accuwedge to tighten it up a bit. When really bad I will change out the takedown and pivot pins with slightly larger diameter ones. It is usually caused by the luck of the draw and tolerance stacking during manufacture of the components.

[Hoot]

The play between upper and lower receiver doesn't mean much to accuracy but it does to my confidence. For that reason I would install an accuwedge to tighten it up a bit. When really bad I will change out the takedown and pivot pins with slightly larger diameter ones. It is usually caused by the luck of the draw and tolerance stacking during manufacture of the components.

I did the oversize pins on one of mine and its as you might imagine, a no-brainer. An Accuwedge doesn't always fit sight unseen. You may find that you have to trim-to-fit a little. To be honest, a little piece of old rubber gasket or any number of other things will work just as well.

Hoot

[bushmeister]

I didn't like the slightest noise mine made so I put an accuwedge in it and never looked back.