View Full Version : Colt AR15 early (SP1) receivers....compatible with newer upper receivers?

12-02-2006, 1:58 AM
I have two (legally registered lower receivers with DOJ...have the letter to attest), and am considering of upgrading these early (4 digit serial numbered) Colt AR15 SP1 receivers with something newer \ accurate.

Will I have any problems simply removing the old upper receiver and installing the new upper receiver without having to do any modifications to either receivers?


San Diego

12-02-2006, 5:58 AM
Well they are possibly large hole lowers, which means the front pivot pin is bigger than .25 but there are adaptors to make them work.

Bring in your lowers to the Del Mar Show and we'll get a good fit for you......:D

12-02-2006, 6:03 AM
Wow, too bad those aren't transferable.

I'd love an early Colt lower for my "new" A1 upper.