I have a Colt HBAR I bought in March and I want to have an upper receiver to change out from the standard A2 it came with. I've heard that Colt's take down pins were different size's than every one elses, I'd like to have a varmint upper for it, just to tinker with. But I want to shy away from buying from Colt only from what I want.
Look forward to hearing from all of you.
Semper Fi,
Keith
Sgt USMC

Some colts have mil spec take down pins( I know late blue labels do, and early guns, also.).  If your front and rear are the same size they are mil spec.  If not, the front will be larger.  In this case, You can buy a conversion pin to fit mil spec uppers.  I do not know the quality they offer, but are quite common.  Get you a conversion pin and put on whatever upper you desire!!!!

Caden

If you bought it new, this March, it should be standard "small" pivot pin.

Only goofy pins on the thing would be the fire control pins - hammer & trigger.

Good luck

Early guns ESPECIALLY have large pivot pins.  Colt was worried about people using M16 uppers since day one.  Right before the ban, blue labels came out with small pins, I think they've been that way since.