Colt BCG Difference

[mag318]

The Colt 6920 I just bought has an unusual, to me, BCG. I compared it to another 6920 and the rear of the BCG is machined open on mine and closed on the other. My question is why the difference, these are both factory Colt bolt carriers?
I have owned several ARs and they have always had closed not open bolt carriers. With the wealth of knowledge of forum members I knew this is the place to find out about these Colt bolt carriers.

[ThirdWatcher]

How old is that 6920? I've never seen a 6920 with that kind of BCG. (My 6520 came with one of those and I installed a BCM FA BCG before I ever took it to the range.)

[Cagemonkey]

Did you buy a new or used rifle? Those type of BCG's were used in Colts that had the sear block in the lower receiver. I can't imagine one of those being put in a current, factory new Colt 6920 unless the factory was scrounging for parts.

[ThirdWatcher]

My guess is someone took the FA BCG after it left the factory and substituted the neutered one.

[sanman96825]

I have an older A3 (~12 years old) that has no sear block but has the half moon BCG. Guess I'm just "unlucky" lol

[C-grunt]

If thats a newish rifle I think someone swapped it out on you. I had that in my older 6520 that had the bif fire control pins and big front takedown pin.

[usmcvet]

There is a good BCG sticky you could read up one here. I think Robb wrote it. I'd call Colt to confirm it but looks like some one pulled out the new FA BCG on you. Is it a brand new gun? If so I would contact the person who sold it to you and ask for a Colt FA BCG. They also may have ordered it that way. A local class 3 dealer here in VT told me I could not have a FA BCG in my semi AR, he was wrong but arguing just wasn't worth it. My LMT factory SBR came with Semi BCG.

[JStor]

Right when the 1994-2004 "ban" reached its sunset, I believe the 6920s were still being furnished with the neutered bolt. Mine came that way, and I later replaced it with a full weight carrier.

My MT6400C also was furnished with the trimmed carrier, and I replaced that carrier also. Sometime after 2004 and early 2005 as my best guess, they all came with the M16 carrier...even the 6724 varmint model.

[RichDC2]

what is the date on the barrel?

[mag318]

Thanks guys for all the replies. The Colt 6920 is an older one I bought last week that was modified into a 6921. I posted pics under Colt 6921 in the AR General Dicussion forum here. Though used the carbine is in new condition so I'm not worried about how this bolt carrier will function as it is a factory carrier. I was just curious as to why it was machined like that and I appreciate the answers.