12-13-2013, 01:39 AM
The area where the lapping tool contacts your upper's interior is already subject to reciprocating friction from the BCG, as well as contact with the barrel extension. Also, the application of a good light oil on the lapping tool should go far in mitigating any incidental wear you might incur when using it. In the grand scheme of things, though, any wear from the lapping tool is in the noise, compared to what happens under normal operation. Further, don't overlook the fact that the anodized component of the upper is being deliberately removed at the mating surface. I've never seen any signs of corrosion with any of my lapped uppers, whenever they have been torn down for any reason. I invite the metallurgists in the Horde to comment further, and perhaps add insights on assembly greases.
I personally don't like making any assumptions about how straight anything is. If you wish to verify, a very few rotations with the tool will quickly reveal how square your upper is. (Refer to LRRPF52's photo, in post #1, as an example.)
As far as fitting your barrel to the Mega Billet upper goes, I seem to remember someone mentioning that they had to put their barrel in the freezer and, just before installing it, they put the upper in an oven. I further remember the OP had called the mfgr, who told them to do this. Anecdotal, to be sure, but that's how I remember it.
I personally don't like making any assumptions about how straight anything is. If you wish to verify, a very few rotations with the tool will quickly reveal how square your upper is. (Refer to LRRPF52's photo, in post #1, as an example.)
As far as fitting your barrel to the Mega Billet upper goes, I seem to remember someone mentioning that they had to put their barrel in the freezer and, just before installing it, they put the upper in an oven. I further remember the OP had called the mfgr, who told them to do this. Anecdotal, to be sure, but that's how I remember it.