Hi guys! I have a couple of questions for you. I have an old Colt SP-1 Upper reciever and I was thinking of putting one of Bushmaster's Disippator barrels on it. Does anyone know if I would have any difficulty fitting a Bushy barrel on this upper? If you could provide some answers here I'd appreciate it. I have heard that with new Colt stuff they are making it out of spec so you can't mix and match parts, not sure if is true or not and if so whether it extends to older recievers.

You should have no problems swapping the barrels on your upper. I don't believe Colt has altered their uppers from the standard specs yet.

Given how cheap uppers are though, you may want to just buy another upper. Your SP1 upper might be more valuable the way it is. You may want to check into that first.

Ditto; no problem.