I have a pre ban PWA lower(new never used)with a new LMT M4 upper.It has some wobble that really bothers me.Most of it comes from the front pin area.Any way to tighten that up?

Yes, o-ring over the front lug on the upper.

 

http://www.ar15.com/forums/topic.html?b=3&f=118&t=535643

Do this.....

What size o ring is that?

I'd like to know also.I used an o ring,but it was too tight.

hit up an Ace or True value and just get a whole bunch of them in various sizes.  They are like $0.17 each.

I did the O-ring thing for a while, but the ones that made the gun tight eventually ground up or broke.  They looked like they had the potential to enter the action and possibly get stuck in the BCG channel.  Most likely any debris would get shot out, but why take the risk.  I just learned to live with the minimal wobble.   I don't even notice it anymore.

Just got back from Ace,.69 cents later i'm a happy camper!The size is 9/16x3/8x3/32.Fit's PERFECT and doesn't squeeze into the magwell(like the next size up did).I know it doesn't do shit,but it REALLY bugs me when it's rattling around.Feels cheap,like an AK or something....

Hey now, only the parts inside an AK rattle around

I was considering cutting some gasket material and trim-taping it there. Like most, mine has the slightest of play, so it's not really a concern.

I had a little wobble in one of my target rifles, so I got some sheets of shim material for press brakes, and cut a small filler disks for the sides of the front lug, and a little square U shaped pad back contact point of the receiver to go under the rear lug.  The fit is ROCK solid, without any wiggle at all.  I know it didn't effect accuracy, or performance to any degree, but it was driving me nuts.

You can get high strength plastic (I went with this) in .0001 to .0020 thicknesses, or stainless steel in .00005 to .0010 thicknesses.  

It won't wear out like an o-ring can, doesn't compress, and when you have the right thickness, it's perfect.

Just don't forget it's there when you clean it, and be careful with the SS sheet.... If you thought a paper cut is bad, you don't want to see what .00005" thick stainless can do.

JB weld. "Bed" the upper to the lower.

Pics?

 

Double check your mags drop free tomorrow, especially Pmags.  Mine did at first but after a day, the O-ring stuck out and they wouldn't drop and then went to a smaller size.

Sure.  The idea is to degrease the upper and wax the lower.  For the upper, cleaning with non-chlorinated brake cleaner and a brush (test solvent compatibility before using) is a must, this is where the JB Weld will adhere.  Wax the lower with Johnson's Paste Wax and let dry before buffing.  



Mix the epoxy to directions, using the slow cure original.  Apply to the upper, where it contacts the lower, including the back curved part.  Let it set up 20 minutes or so, this helps.  Then assemble the rifle, cleaning up any squeeze out and let it set up for 24 hours.  Remove both pins and clean up the squeeze out from the inside, using a knife made from scrap brass cartridge case.  It won't scratch the aluminum.

















When done correctly, it cannot be seen assembled.  And it doesn't impair anything other than it might prevent exchange between rifles.  It does stop all wobble.



 

Cool, thanks. I was envisioning a small bump of it somewhere. I'm glad a little wobble doesn't bug me, that looks like a lot of work

 

Work?  Gee, it isn't rocket surgery.  And it is the best solution since it doesn't put any stress on the upper or lower, unlike the o-ring method or Accu-Wedge.  It adds a trivial amount of weight and keeps dirt out.



 

Well I'm no rocket surgeon, but I don't mind a little clickety-clack between receivers.