AR 15 Bolt Carriers.

[cape cod basser]

Rebuilding an AR for a friend that had an A-2 version with carry handle that he has never shot. He bought a thermal imaging scope that is unbelievable so I needed to set the gun up as a flat top with free float hand guard and rail.
I started with a complete upper from Palmetto similar to this one, http://palmettostatearmory.com/psa-1...516446756.html
Added a BCM Extended release charging handle and figured I was done.
Once assembled I noticed the bolt carrier was snagging half way to close, and it was not normal so I dug into it further.
Turns out it was a Colt original bolt carrier which has the section on the bottom that would normally cover the head of the firing pin removed, so when the bolt carrier slid across the hammer it was hanging up on the head of the firing pin with the tighter tolerance of the new upper.
(Would not do it with the original A-2 upper installed).
Does anyone know of these bolt carriers? Just curious of the reason to uncover the head of the firing pin. All I can figure is that it would help with a quicker recovery during full auto fire maybe?
I ordered a new Nib bolt carrier from Aim Supply and left the old one with the original upper, but was just curious about the original carrier.

[Hickory Legend]

So is this a Colt rifle?

They don’t play well with mil spec parts!

[Sabre Fan]

I agree with Hickory Legend.

Also, a new bolt should be purchased any time a new bolt carrier is purchased. Those tolerances are so tight that they tend to break in "together". This is just a rule of thumb, but not always the case.

Maybe the old bolt will fit fine in a new carrier. Just something to check during the assembly and functions check.

Good luck, sounds like a great rifle!

[cape cod basser]

Bought a complete bolt carrier for a replacement. Nib from AIM Surplus...
Does not say Colt anywhere but have my suspicions...

[Sabre Fan]

I think the FN and Milspec parts are usually interchangeable. Colt tends to do it's own thing. Most of the rifles I carried in my 20 years were FN (M16A2 and M4 variants). I carried an M16A1 from 86-88 and I don't recall who made them.

I'm thinking you'll be ok with your new carrier assembly.

[Hickory Legend]

Bought a complete bolt carrier for a replacement. Nib from AIM Surplus...
Does not say Colt anywhere but have my suspicions...

What about the lower, what is stamped on it? Is it colt?

If not I would try a non Colt carrier bolt and see how it cycles.

[cyclone70]

Many revision changes were made to parts since the original A2 guns.
Replacing the original hammer may help solve some of the problem.
I believe the later hammers were ramped slightly to help this.
The original metal A2 mags may drag on the bottom of the newer BCG also.
Keep in mind that many of the early guns required them to be cycled hundreds of times
to get the gun to function reliably.

[cape cod basser]

Many revision changes were made to parts since the original A2 guns.
Replacing the original hammer may help solve some of the problem.
I believe the later hammers were ramped slightly to help this.
The original metal A2 mags may drag on the bottom of the newer BCG also.
Keep in mind that many of the early guns required them to be cycled hundreds of times
to get the gun to function reliably.

Thanks Tyler.
I shot the gun before removing the original upper and it did NOT like the metal mag that was with it. I had to use my ten round P-Mags.

[Igore67]

Is it an 'SP1' style carrier? These parts can fetch petty good coin. How old is this rifle?

[cape cod basser]

The one I have looks like the M-16 carrier and the bottom is like the SP1. When the bolt carrier was dropped in the new upper, the back of the hammer was catching on the head of the firing pin...