RE: OK to remove barrel after sighting in?
If you have a cantilever mount and the scope comes off with the barrel, you would probably be ok.
If you're using a saddle mount over the receiver, then you might have a problem.
Mine has a saddle mount and I try not to disassemble it unless absolutely necessary.
I do lay 2 or 3 layers of duct tape on the back end of the Hastings barrel and then cram it into the 1100's receiver so as to eliminate any slop.
It usually goes back close enough that I can still hunt with it if I don't have a chance to check it.
It will lay 3 regular Brennekes touching at 100 yds. and Hornady's H2K Sabot will have 5 shots inside a 3 inch circle at two hundred yards.