Stevie Boy
Ultimate Member
Looking to pick the MDS brain trust again. I feel more comfortable asking here than arfcom but I may also pose this to the SOTAR facebook page.
Later this summer, I have it in my head to start a new build for a “more accurate” AR 15. Not necessarily match grade mind you but better components (primarily barrel) to improve accuracy. So, my plan is to combine a BCM upper with a Criterion barrel and a Geissele gas block as the primary components of the upper. My questions are as follows.
With respect to bedding the barrel, I’m prepared to lap the upper. Given what I hear about BCM uppers being tight fits, I’m expecting to have to do a thermal fit of the barrel. Just so I’m clear, if going that route, no Loctite 620, Rockset, etc. is needed. Correct? I also expect that I may well need to heat the upper to get the lapping tool to fit. Anything else I need to watch out for? Or, am I off base?
Regarding the gas block, when Chad posted those videos from Criterion about accurizing the AR, Criterion clearly said that they don’t recommend pinning the gas block. Pretty sure I’ve seen/read elsewhere that the Geissele gas blocks are relatively straightforward to pin without special tools even though they’re set up for set screws. I think they call it “bomb proofing”. So, to pin or not to pin? That is the question. If pin, has anyone on here done it with the Geissele GB? Usually you can find youtube videos for just about anything but my searches have come up empty.
Fwiw, this will be my first upper build. Done a number of lowers but always steered clear of building my own upper. But, in retirement, I’m looking to try something new.
Later this summer, I have it in my head to start a new build for a “more accurate” AR 15. Not necessarily match grade mind you but better components (primarily barrel) to improve accuracy. So, my plan is to combine a BCM upper with a Criterion barrel and a Geissele gas block as the primary components of the upper. My questions are as follows.
With respect to bedding the barrel, I’m prepared to lap the upper. Given what I hear about BCM uppers being tight fits, I’m expecting to have to do a thermal fit of the barrel. Just so I’m clear, if going that route, no Loctite 620, Rockset, etc. is needed. Correct? I also expect that I may well need to heat the upper to get the lapping tool to fit. Anything else I need to watch out for? Or, am I off base?
Regarding the gas block, when Chad posted those videos from Criterion about accurizing the AR, Criterion clearly said that they don’t recommend pinning the gas block. Pretty sure I’ve seen/read elsewhere that the Geissele gas blocks are relatively straightforward to pin without special tools even though they’re set up for set screws. I think they call it “bomb proofing”. So, to pin or not to pin? That is the question. If pin, has anyone on here done it with the Geissele GB? Usually you can find youtube videos for just about anything but my searches have come up empty.
Fwiw, this will be my first upper build. Done a number of lowers but always steered clear of building my own upper. But, in retirement, I’m looking to try something new.