I have two SBRs both in 223, one in 14.5" the other 10.5", both with different dedicated lowers and serial numbers. I have the tax stamp for both, so i am good as far as that goes. I also have a standard 16" AR15. I want to get a 300BLK upper in 10.5", a 9mm upper in 10.5", and a CMMG .22...