Upper Receiver????

[A5BLASTER]

I have a few questions for A5BLASTER...

1) Is a .997" diameter barrel extension undersized? 2) What material do you use for shim stock when needed to bed the barrel extension... steel or brass? What shim stock thickness do you normally use for this bedding? I have steel .001" to .010" thick.

Dont know, never measured any of my barrel extensions.

I check to see if it will go in by hand, if it does, I get a piece of .003 thickness steel shim stock and check it. If it still goes in I get a peice of .005 shim stock.

Never used a peice thicker then that.

I then get the shim trimmed how I like and then freeze the barrel for about 2 hours and then heat the upper, then install it and leave it alone too return to room temperature. Then I install the barrel and barrel nut.