What causes reciever wobble? [Archive]

kwelz

10-19-11, 14:53

First off let me say that receiver wobble isn't something that bothers me. I have guns that are tight and guns that shake. I have never found myself caring one way or another.

However I am curious as to what causes it. Is it the size of the hole for the pins? The way the upper locks into the lower? Some combination thereof?

Iraqgunz

10-19-11, 14:57

Off the top of my head it's the fit between the rear lug and the rear of the receiver. I would think that the pin could play a small role as well. Basically if you take a tight upper (like my Vltor MUR) and you mate it to my lower you can see how the lug mates up and because it is such a tight fit, it cannot move.

amac

10-19-11, 21:48

Mega lowers offer a tension screw that presses up against the rear lug. The screw is under the grip. It's a simple way to tighten up the waggle that so many AR's are known for. The wobble drives me crazy, but then little things like that should be overlooked according to many people on this forum. :eek: Slap some gum in there and you're GTG! :D

J8127

10-20-11, 09:58

I don't like the wobble either, but I accept that it is neither an indication of quality or has any effect on accuracy/reliability.

polymorpheous

10-20-11, 19:13

I believe the OP was asking what caused the wobble from a technical standpoint.
Not how to be rid of it, or how one feels about it.

Kwelz, my money would be on dimensional tolerances.
I can dig up a print for a lower, (not sure if I have one for an upper), and tell you the dimensions and the +/- tolerances for the front and rear lugs. Give me a minute...

kwelz

10-20-11, 21:58

I believe the OP was asking what caused the wobble from a technical standpoint.
Not how to be rid of it, or how one feels about it.

Kwelz, my money would be on dimensional tolerances.
I can dig up a print for a lower, (not sure if I have one for an upper), and tell you the dimensions and the +/- tolerances for the front and rear lugs. Give me a minute...

Correct. Unless it is an obscene amount of receiver wobble the only time I notice it is when handling the gun cold. I don't really care as long as it doesn't interfere with function.

polymorpheous

10-20-11, 22:09

I do not have a upper drawing.

On the lower, the dimension inside to inside of the pivot pin boss is .500" +.000 -.002"
The rear is the same.
The dimension of the front and rear pin center to center is 6.375".
Everything zeros off of the center of the pivot pin on the drawing.