2 New Grendel Builds - 16" Hunting Rig & 10.5" Pistol

[BlogSarge]

What do you mean “bed the uppers?”

It can be done a few ways. Numbers 1 and 2 below are technically thermo-fitting.

1- find a tight upper receiver (like BCM) and you will have to heat the upper receiver barrel extension (to expand it), and freeze the barrel’s barrel extension (to contract it) and then quickly mate the two together.

2- if you have a looser fit, you can use uber-thin shim stock wrapped around the barrel extension to create a tight fit, then do the above.

3- you can use a LocTite compound to ‘weld’ the barrel extension to the upper receiver.


In any event, the purpose is to eliminate any wobble or play between the barrel and upper receiver.

M4Carbine and Snipershide have some detailed threads, discussions, debates on these techniques’ necessity and how to properly do them.