Does the Colt SP1 offset pin to adapt any upper to the large hole lower work very well?  Is there still some creep in the small pin uppers that are attached, or is it a nice snug and proper fit?



Thanks.

I have several different types and they all work fine. You must be careful when closing the upper to insure it doesn't bind. It is possible to damage the rifle if you aren't careful. Once closed and pinned in place it acts like any other rifle.

Sometimes they adapt one pair of receivers better, or worse, than another.

I have a large hole upper that adapts and opens and closes great to one lower. But for reasons I don't recall I couldn't use it forever on that lower (one of my NoDak Spud retro lowers maybe). So I put together one of my other lowers. There is just enough subtle, manufacturing difference that the two receivers don't close as tightly and the two will not pivot open. To open that gun now I have to punch out both pins. It's still my favorite carbine, a lightweight XM177type clone on an A2 lower, but it does have this little inconvenience about it.

So the adapter bushing/pin may work great for you, or it may not. You won't know until you give it a try.

Speaking of uppers and lowers that dont work, here is a modification I had to make to a keyhole flattop upper to my SBR lower. This was a pain because this is the second upper I purchased for this lower. Before I ordered this upper, all the other uppers I fit to this lower worked (10+) so the key hole upper is out of spec. One was ordered from CMMG one from BCM.  Neither of the fit and both had to be modified.



Anyways, here is the tremendous amount of filing I had to do to get it to fit the SBR lower.

Jeebus, that sucks.

I've never had any problem with mine. There was a little binding at first, but I hit the center part lightly with a Dremel. It doesn't bind, but still offers a tight enough fit.