upper to barrel fit up

[devildogandboy]

Depending on the extension and the extension tunnel on the upper, they can be wobbly or too tight, to the point that you need to heat the upper and freeze the barrel to get a thermo-fit, which when I find that combo, I'm happiest.

Otherwise, it's bedding time for the extension and upper.

just one quick question before i do this method, if i wish to change barrels later i would heat it up and remove barrel? no problems?

Bruce