So my new (old) colt SP-1 has got two different size takedown pins. The front one is slightly larget than the rear. Someone posted .250 and .312 so that might be about right.

So the question is: Is there some sort of adapters to allow attaching uppers with the small holes only, or some other combination?

I have a postban Armalite carbine which has two small holes (.250 I think). Can I get an adapter to attach it to my SP-1 lower assembly? (The rear pin is the right size but the front one is not.)

Offset Pin:
Adapts Colt Lower Receiver (large hole) to M16 forward assist type Upper Receiver with smaller hole. $5.95 from Bushmaster

www.bushmaster.com/shopping/lowers/nes-06.asp