What is the difference between different brands uppers or lowers.  Are they all interchangable?  Also whats the difference between a one stage and a two stage trigger?  Thanks

Hello, anyone out there???

Most of the lowers and uppers are interchangeable. Just some of the Colts have a large hole for the takedown pins that will need a special pin. All small hole will interchange. Mil-spec does that for you....  

Can't exlpain much about the trigger... fullclip

OK difference between a 1 stage and 2 stage trigger is exactly as it sounds.  On a standard combat rifle the trigger pull is supposed to be about 4.5 lbs of pressure before the trigger "breaks" and the hammer falls causing ignition.  On a single stage trigger you will pull thru the entire 4.5 lbs.  On a 2 stage trigger there are 2 stages. The first being approx. 2.5 lbs. when you reach the 2.5 lbs of pull you'll feel a click.  Then you onto the second stage which is usually 2 lbs.  On the second stage the trigger breaks and the hammer falls again causing ignition.  Basically a 2 stage trigger is more accurate as it is easier to pull.  For you recreational shooter and combat shooter a single stage is more then adequate.  For your competition shooter DCM and such, a 2 stage trigger is almost a neccesity.  Hope thet helps.

Hey, thanks for the information it was very helpful.

Welcome, where do you live?  Nothing like some hands on experience.  

Many local groups get together and shoot, drink/eat and generally b.s.

I live in San Antonio.  Is there anyone close to me??