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Bauer C
08-20-12, 15:35
Just finished a new upper and wanted to see what you thought.

With a round chambered, the force needed to pull back the charging handle to extract the round is much more than with my other rifles. It feels like the cam pin might be sticking a little but i am not certain.
Hand cycling empty it moves smooth.

It is a new Bushmaster BCG (blue extractor) in a new BCM upper.
ForTehNguyen
08-20-12, 18:05
it will smoothen up as you shoot it. My DD upper was rough when new but after shooting a few hundred rounds, it smoothened up a lot
cbr
08-20-12, 18:24
"It is a new Bushmaster BCG (blue extractor) in a new BCM upper."
:mad: Here is your problem!
ST911
08-20-12, 18:48
Test fire it. If functional, don't worry about it, and refer to the "oh no, I bought a..." thread for prudent PM.
SomeOtherGuy
08-20-12, 19:42
Just finished a new upper and wanted to see what you thought.

With a round chambered, the force needed to pull back the charging handle to extract the round is much more than with my other rifles. It feels like the cam pin might be sticking a little but i am not certain.
Hand cycling empty it moves smooth.

It is a new Bushmaster BCG (blue extractor) in a new BCM upper.

1) I'm used to stiff cycling with new DD BCGs and it goes away with some use, as noted.

2) The fact that your BCG is stiff with a round chambered and not with chamber empty is different from my experience. Makes me wonder if there could possibly be tight headspace - not common for an AR, but possible. What's the barrel in your build? Have you checked headspace?

3) If no obvious defects, I would shoot it and see if it smooths up from use.
Iraqgunz
08-20-12, 19:47
Believe it or not, BCG's can be out of spec. We have specific gages to measure things like inner/outer diameter, gas key, etc...

OP,

I am curious. Why would you put a BM BCG in a BCM upper? I would immediately replace the screws and the extractor spring assembly.

My guess is that it is stiff for a variety of reasons. Once being that you are slowly hand cycling the BCG and you probably have very little lube on it.
Bauer C
08-20-12, 21:21
I got the BCG as a part of a trade a while back and figured i would put it to some use. As for the lube, I keep my bolts well oiled, and used some grease on the cam area and on the carrier rails.
munch520
08-21-12, 12:32
Test fire it. If functional, don't worry about it.

Agreed - curious to hear what you figure out OP
Bauer C
08-21-12, 19:26
Believe it or not, BCG's can be out of spec. We have specific gages to measure things like inner/outer diameter, gas key, etc...

OP,

I am curious. Why would you put a BM BCG in a BCM upper? I would immediately replace the screws and the extractor spring assembly.

My guess is that it is stiff for a variety of reasons. Once being that you are slowly hand cycling the BCG and you probably have very little lube on it.

Is there a known problem with the gas key screws? It looks like one is marked "fmx" and the other is blank. The staking was very light and in between the screws outer edge and the key, so I added side stakes with my auto punch.
Freedoooom
08-21-12, 19:50
Check the charging handle.
Iraqgunz
08-21-12, 21:00
I would replace the screws with quality ones from Colt and then re-stake with a MOACKS or the field staking method.


Is there a known problem with the gas key screws? It looks like one is marked "fmx" and the other is blank. The staking was very light and in between the screws outer edge and the key, so I added side stakes with my auto punch.
Stickman
08-21-12, 23:27
I am curious. Why would you put a BM BCG in a BCM upper?

I really wish guys would either ask the board, or find a few people who knew what they were talking about and ask them.