Swaping AR BCG's

**QuackXP** · August 20th, 2013, 11:42 AM

I have a Colt AR-15 model 6920 and I recently got a PSA BCG for a future build and as a backup to the Colt.

I cleaned and lubed the PSA BCG and it fits in the Colt upper but when I slide it in and out it takes a slight bit more pressure at one spot. When I have the upper attached and use the charging handle I don't notice any difference other than the Colt BCG is smoother.

Would there be any issue in firing the Colt with the PSA BCG in it? Is this common when inserting a factory fresh BCG in a firearm that has been run for a few thousand rounds and its previous BCG has worn in with the upper?

I know that AR parts if built to spec should be interchangeable, it does not feel like its binding up just a bit more friction at one point at the far end of the travel.

**ithinkimamedic** · August 20th, 2013, 11:47 AM

You should have no problems using the PSA BCG in your Colt. That little binding feeling you have is likely a result of new parking on the bolt and if you were to run it in that gun for a little would go away, the fact that you don't feel it when using the charging handle supports this. Always a good idea to have extra parts around and test fitting them is also a great idea, hell I wouldn't fault you for testing it for a few hundred rounds just to make sure that the PSA BCG doesn't have an immediate failure.

**Hawk** · August 20th, 2013, 12:50 PM

It's my understanding that the bolt can affect the head space on a AR. Yes, theoretically they should all be interchangeable, but sometimes they aren't.
I was shopping for a replacement barrel for my AR a few years ago, two of the vendors I was talking with included a matching bolt (not BCG) with the new barrel. Try using the Colt bolt with the new BC and see how it feels.
Shooting it and inspecting the brass will be the final determination.

**ar15jules** · August 20th, 2013, 12:55 PM

Originally Posted by Hawk

It's my understanding that the bolt can affect the head space on a AR. Yes, theoretically they should all be interchangeable, but sometimes they aren't.
I was shopping for a replacement barrel for my AR a few years ago, two of the vendors I was talking with included a matching bolt (not BCG) with the new barrel. Try using the Colt bolt with the new BC and see how it feels.
Shooting it and inspecting the brass will be the final determination.

A NO GO or FIELD GAUGE might be handy....Although I doubt he will have any serious issues.
Jules

**Splittiebus66** · August 20th, 2013, 01:04 PM

From what I've seen, new BCGs can be surprisingly stiff. If you want, take the thing and manually work it for a while by hand and it will loosen up. You could just shoot it as well, I'm pretty confident you are OK

**625** · August 20th, 2013, 01:33 PM

Originally Posted by QuackXP

I have a Colt AR-15 model 6920 and I recently got a PSA BCG for a future build and as a backup to the Colt.

I cleaned and lubed the PSA BCG and it fits in the Colt upper but when I slide it in and out it takes a slight bit more pressure at one spot. When I have the upper attached and use the charging handle I don't notice any difference other than the Colt BCG is smoother.

Would there be any issue in firing the Colt with the PSA BCG in it? Is this common when inserting a factory fresh BCG in a firearm that has been run for a few thousand rounds and its previous BCG has worn in with the upper?

I know that AR parts if built to spec should be interchangeable, it does not feel like its binding up just a bit more friction at one point at the far end of the travel.

Did you get one of the more expensive full auto BCG's or the cheaper P-TAC one? I ask because I bought the cheaper one as a spare for my plinker and would let you know how mine fit since I should have mine at my door when I get home.

**QuackXP** · August 20th, 2013, 01:36 PM

I got the cosmetic blemished PSA full auto BCG. The only blemish was some discoloration and not on the rails that the BCG rides on.

**ithinkimamedic** · August 20th, 2013, 02:37 PM

Originally Posted by Hawk

It's my understanding that the bolt can affect the head space on a AR. Yes, theoretically they should all be interchangeable, but sometimes they aren't.
I was shopping for a replacement barrel for my AR a few years ago, two of the vendors I was talking with included a matching bolt (not BCG) with the new barrel. Try using the Colt bolt with the new BC and see how it feels.
Shooting it and inspecting the brass will be the final determination.

Yeah, the bolt itself would affect the headspace but changing the carrier should not. Excellent suggestions on the testing of it I feel.

Originally Posted by ar15jules

A NO GO or FIELD GAUGE might be handy....Although I doubt he will have any serious issues.
Jules

bingo!