BCM thermo fit upper fun

[Old Bob]

Three cold water actually helped because after a while the barrel extension would heat up and the thing would no longer budge. Definitely doing the freezer next time.

I recently installed a loose fitting barrel using the thermal method & .002" stainless steel shim stock. The cold barrel went in only so far into the heated upper before I could no longer push them together by hand. It was about a quarter inch shy of being fully inserted so I threaded on a barrel nut & used that nut to pull the barrel the rest of the way into the upper. Torqued to 45ftlbs it's a good, tight, solid connection. Here's hoping it will shoot gnat's eye groups.