BCM M4 Upper Receiver Assembly
Jun 2nd 2020
for barrel extension slightly undersized for a tighter fit on the barrel,
and a more accurate rifle.
On a precision made milspec upper receiver like the BCM4
Upper you purchased, you will need to apply heat with a heat gun to the barrel
extension aperture on the receiver.
Simply apply heat with a heat gun to the forward end of the upper and the
barrel will slip right in.
a very tight hold on the barrel and eliminates the need for bedding of any
All BCM® complete upper receiver groups are
built with the very same upper receiver forgings like the one you