Troubleshooting a new build, think I got it figured out.

[Jmedic_]

I can't believe people still dick with O-rings.

Why is that?

[friendlyfireisnt]

Why is that?

Because the O-Ring was simply an interim solution for the military, not a permanent one. A heavy duty spring is a better long term solution.

The O-Ring works, but it's best as a temporary measure or for troubleshooting, like I did here.

That said, with the exception of the 3 BCM BCG's I have, I couldn't tell you until this week what spring/O-ring combo was in my Larue, or Rainier or my sole PSA BCG's. I still don't know whats in my LMT BCG (but will be looking tonight).

And that's because traditionally, they worked. If it works, I generally don't mess with it. Once I find something that isn't working, then I look at the solution. Now that I have identified a failure point, i will begin replacing the springs, and testing it in my various AR's.

This is the first time I have had failures of this sort with one of my own rifles.

[Jmedic_]

Because the O-Ring was simply an interim solution for the military, not a permanent one. A heavy duty spring is a better long term solution.

The O-Ring works, but it's best as a temporary measure or for troubleshooting, like I did here.

That said, with the exception of the 3 BCM BCG's I have, I couldn't tell you until this week what spring/O-ring combo was in my Larue, or Rainier or my sole PSA BCG's. I still don't know whats in my LMT BCG (but will be looking tonight).

And that's because traditionally, they worked. If it works, I generally don't mess with it. Once I find something that isn't working, then I look at the solution. Now that I have identified a failure point, i will begin replacing the springs, and testing it in my various AR's.

This is the first time I have had failures of this sort with one of my own rifles.

Interesting. I'm curious as to why BCM told me to make sure both are installed when I emailed them.

[tehpwnag3]

Most likely a better safe than sorry approach.

Interesting. I'm curious as to why BCM told me to make sure both are installed when I emailed them.

[Jmedic_]

Most likely a better safe than sorry approach.

I'm not disagreeing w/ you. But, let me play devils advocate. If using the O-ring causes the problems that people are saying it does, wouldn't everyone running their BCG's w/ the O-ring be complaining etc and then I would think they would either A) have to stop installing them in their BCGs during assembly or B) tell people they need to remove them once they purchase them, since it is an extra failure point?

[tehpwnag3]

Don't know about everyone else, but I've never had problems running with an o-ring. In recent years, with companies making the highest quality springs we've probably ever seen, I've been doing away with the o-ring and replacing the stock springs with upgraded springs. Haven't looked back. YMMV.

ETA: Let me clarify "never had problems". I've never had malfs contributed to them. I do routine maintenance on all my weapons and if I noticed an o-ring getting worn/soft/chewed, I replaced it without a second thought.

[titsonritz]

Why is that?

From the BCM web site:
"The BCM Extractor Spring is so strong the Mil-Spec Crane O-Ring will probably not be needed, but it is included."

As mentioned above, O-rings are nothing more then a stop gap to the correct solution, which is the correct extractor spring & extractor insert. If a BCG came with inferior parts or either of those parts are worn to the point where an O-ring is needed then replace them.

[friendlyfireisnt]

I'm not disagreeing w/ you. But, let me play devils advocate. If using the O-ring causes the problems that people are saying it does, wouldn't everyone running their BCG's w/ the O-ring be complaining etc and then I would think they would either A) have to stop installing them in their BCGs during assembly or B) tell people they need to remove them once they purchase them, since it is an extra failure point?

The O-ring doesn't cause issues, unless you also have an upgraded spring.

Generally, you either want an upgraded spring with the black insert, or you want a standard spring with the black insert and an O-ring.

It's generally an either/or option normally.

[friendlyfireisnt]

As a resolution, I replaced the extractor spring with a BCM kit, sans O-ring. Also replaced the springs in 4 other BCG's that didn't have upgraded springs.

Today, took the carbine to the range, and shot 120 rounds trouble free. While that's not a lot of rounds, it was just a test to verify that the upgraded spring would solve the issue. Next I will be testing different buffers.

Planning on taking this carbine to a class in February, goal is to have at least 500-600 rounds through this carbine prior to the class.