AR15 barrel extension wiggleage

[sentry1]

I recently swapped out my A2 handguard and whatnot to put a Midwest Industries free float tube on my AR15. With the barrel out to replace the barrel nut, I discovered that the there is a LOT of wiggle room between the barrel extension and the receiver. I.E. the outer diameter of the barrel extension is smaller than the inner diameter of the receiver.
Is this normal?

Also, not a functional problem, but I wish I'd known it would happen, the top rail on the MI tube is about 2mm (just used calipers, it's actually 0.8 mm) lower than the rail on the receiver. Is this a design issue like with the DPMS high/low height change?

 

[Glen Seekins]

Re: AR15 barrel extension wiggleage

It's normal. I have seen barrel extensions vary quite a bit. Idealy they are a tight fit, but mill spec tolerances are loose so they always go togeather like Lego's

 

[sentry1]

Re: AR15 barrel extension wiggleage

Well, if that's the case, no biggie then. Any idea on the rail height? Do they vary much from receiver to receiver?

 

[BCP]

Re: AR15 barrel extension wiggleage

My Midwest rail was a little lower than the receiver rail maybe half a millimeter. My troy lines up a little lower too. I would not worry about it.

For the barrel you could put some grease or loctite on the barrel extension before sticking it in the receiver.

 

[strat81]

Re: AR15 barrel extension wiggleage

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sentry1</div><div class="ubbcode-body">Well, if that's the case, no biggie then. Any idea on the rail height? Do they vary much from receiver to receiver? </div></div>

Sounds like a tolerance stacking issue. It should not be a problem, but this is why you don't "bridge the gap" with scopes (i.e., mount a ring on the receiver and a ring on the handguard).