Colt pin size confusion

[canadianshooter]

I've been reading older posts regarding Colt pin sizes but am getting confused. Here's the question, I've got a Colt AR-15A2 Government model and I want to put a RRA two stage trigger in it and get another upper(s) for it of different makes. What do I have to be concerned about regarding pins. Will some uppers not fit on it, or can I use an adapter (for the takedown pin)? Thanks.

Andrew

 

[BattleRife]

Your trigger pins should be fine. If in doubt, measure them. I believe standard pins are 0.154", while Colt Special pins are something like 0.172".

Your front receiver pin will likely not be standard. Most likely, it will be two screws that thread together. Any upper you buy will be standard and will require an adapter to fit the Colt lower.