Looking at a Colt AR,

[silverbull]

I have my eye on a Colt AR15, 16" Pencil BBL, Old Style 2 Position Butt Stock, No Forward Assist, A1 Sights in very good condition, with a verified round count of under 500 (I know and trust the original owner)

My questions are, is there any difference besides small hole lower Colt receiver and anyone else's large hole receivers? Is their anything I need to know for upgrade purposes or watch out for regarding Colt AR's?

I'm looking at keeping the 16" Upper and adding a 22" Match style Upper and a competition trigger, maybe some other goodies as well.

 

[Kenneth Lew]

Colt is the only company that made a large pivot hole receiver. This will require the use of an adapter to fit std. spec. uppers to the lower. A pain in the butt to do due to the design.

http://www.ftfindustries.com/Mercha...&Store_Code=FI&Product_Code=M1S-Coltoffsetpin

You are better off getting a std. small hole receiver.

 

[Don't Tread On Me]

You should be good to go. If there are pin-size issues, then consider getting the adapter pins. Bushmaster sells these on their website. They aren't expensive.

 

[R. W. Simms]

The large pins on the Colt are not much of an issue. If you don't like the screw pins then Brownell's makes a replacement push-pin for the Colt .315" pins. Personally, I have never found the screw pins to be problematic although I suppose it could be a hassle if you had one lower serving as the platform for two or more uppers.

Mixing Colt lowers with aftermarket uppers (or vice versa) will work, but I find it less than satisfactory. The axes on the small pin and large pin receivers are not co-linear. To mix uppers and lowers requires the use of an offset adapter pin (or bushing). These pins allow the upper and lower receivers to maintain alignment when closed, but they don't allow easy opening unless there is a lot of slop present. On receivers with a tight fit binding will occur. This is more noticeable when using Colt uppers on aftermarket lowers (bushing required) than the other way around (offset pin required). It's not a huge problem though; you just remove both the pivot pin and takedown pins at the same time and the upper and lower separates easily.

I have both Colt and Bushmaster carbines. Pin sizes aside, if the question is what differences exist between the Colt AR lower receivers and aftermarket lowers then there are others.

- The Colt (AR-15) lacks the raised reinforcement around the mag catch button.

- The Colt lower receiver has less metal removed in the area behind the trigger, making it harder to modify for full-auto.

- The Colt hammer has a relieved face so it won't snag or catch on the bolt carrier or firing pin when the carrier is returning forward.

- The Colt lower receivers are not reinforced in the rear where the buffer tube screws in like some of the modern aftermarket lowers are.

As a side note, the older Colts use 1/12 twist. This is fine with 55 grain bullets but the 62 grain bullets and heavier may not stabilize in this barrel.

These are all pretty minor differences, but Colts are different from the aftermarket lowers in these minor details.

-Bob

 

[richardschennberg]

Are the Colt H-Bars all equipped with 1/12 twist barrels?
Richard
Schennberg.com

 

[Bullet]

Quote - 'Are the Colt H-Bars all equipped with 1/12 twist barrels?"

No they come in 1/9 and I believe 1/7.