Ok, it's been awhile since I've dealt with the whole large pin/small pin issue. I'm looking into buying a Colt SP-1, large pin. Is it the large or small pin lowers that are compatible with your standard mil-spec type uppers like Bushmaster, etc.?

Thanks in advance for your replies.

My Bushmaster has small pin.
I guess if Bushies are mil-spec, then mil-spec is small pin too.

I have a colt A1 upper with a large hole that I'll trade for anything similar with a small hole. It has no forward assist or brass deflector. It does have a new Wilson 16" heavy barrel.

What I did is have a friend make me a bushing to fit in the large hole in the upper, but apparently, the hole in the bushing has to be offset a few thousandths, lest you end up with a gap between upper and lower, and feed problems, like I did. I either need him to make me an offset bushing or trade it for a small hole upper.

You're going to need to use an offset pin to mate your large hole lower to any of the small pin lowers out there. Occasionally, if you look hard enough, you can get lucky and run across a large hole upper for sale.
 I think you can order these offset pins from BM.  I think I've got an extra you can use if you need it.

I have a large hole upper for trade!!! Right here! Large hole upper for sale or trade! I'll take $200 or a small holed upper for it.