Noob question re large/small pins

[Colt]

What's the deal with large pin/small pin setup? I'm new to this and need to put a Colt LE6920 upper on a OLL. Does it matter what OLL I get for pin sizing?

Thanks.

[God Bless The Mauser]

Colt uses large pins so people can't put in the full auto parts. Anything except Colt just uses regular size pins.

[VaderSpade]

Brownells makes/sells a bushing that will fix that.

[VaderSpade]

Link http://www.brownells.com/aspx/NS/sto...PTER%20BUSHING

[goober]

Colt uses large pins so people can't put in the full auto parts. Anything except Colt just uses regular size pins.

different pins. if the OP is talking about pivot & takedown pins (and i think he is),
then VaderSpade is correct, there are pin adapters to compensate b/w the different pin types/sizes. the trick is to find the ones that go in the direction you need (ie big hole in upper, small in lower, vs the opposite).
but i think you (The Mauser) are talking about FCG pins, which also come in two sizes, for the reasons you mentioned. But virtually all common modern lowers use the "small" pins.

[Omega13device]

http://www.biggerhammer.net/ar15/uppers/

Towards the bottom you'll find the discussion of the difference between small hole (milspec) and large hole Colt uppers. Here's an excerpt:

Colt owners often refer to having a small or large hole upper receiver (and corresponding lower receiver). Small hole receivers of .250" are the "milspec", but during early production by Colt for the civilian market, they produced rifles utilizing a .315" spec, so as to preclude use of military uppers on civilian lowers. This production lasted until roughly 1993-1994. As a general rule of thumb all Colt "unblocked" lower receivers, are large hole, while pre-ban "blocked" lower receivers represent transition years where occasional variations popped up.

[Colt]

Thanks, guys. Upper has yet to arrive. I'll check it out next week when it comes in.