AR Screw Pivot Pin / Help

[Fourtyfive]

My Colt AR Sporter Lightweight has a screw head on one side and a head with a flat edge to keep it from turning on the other as a front pivot pin. I am looking into a new upper , does this mean I have the larger pin size ? I bought this rifle under the impression it was a pre-ban. There is no bayonet lug but I think it can still be a pre-ban civilian version ; correct ? What do I need to research as far as getting a new upper for this type of pin ?

I think I read somewhere that RRA makes a conversion detent pin or something but you have to have a detent spring hole drilled ?

[Guest nysos]

Measure it, small hole is supposed to be .250", and the large hole is supposed to be a "double sided" pivot pin with a .312" hole.

As for converting it? I know people do it, mostly with jerry rigged setups - I wouldn't mind using a manufactured conversion kit if it was solid. I personally wouldn't jerry rig something like that.

[Fourtyfive]

So if I want to buy an upper I have to select a pin hole size ? I was under the impression that all were interchangeable.

[Guest nysos]

So if I want to buy an upper I have to select a pin hole size ? I was under the impression that all were interchangeable.

From my understanding, the shape of the pivot pin is the same - it is the exact same design for large hole vs small hole uppers. You don't necessarily have to select a pin hole size, per se. The norm is .250", but there are some that make "large hole" uppers, usually those will be labeled. If it is not labeled or you can't find detail specs, email the company to confirm - it will most likely be .250" though.

I believe it is older colts that have these, same with the large vs small hole lowers for the hammer and trigger pins. Colt tried doing slightly different sizes so that people wouldn't mistakenly slap m16 parts into an ar15, but the industry never went that route.

Edited August 3, 2011 by nysos

[tmedic]

Search colt large hole upper. They make adapter pins and bushings to help out. These links below may help.

AR15Tactical.com - AR-15 Frequently Asked Questions

AR-15 Upper Receiver Comparison and FAQ

[mikegideon]

I put a barrel on one of the post ban Colts for a friend. It had the screw type pivot pin, and was of the large pin variety. IMO, Colt needs to be flogged for the large pin crap. Their idea of a "civilian" AR chaps my butt.

[Fourtyfive]

mmmm hmmmmm......