Crane O ring needed on a middy?

[tom12.7]

When you add additional extractor tension, you add to the sum of required work to properly battery the system. To keep it simple, as an example, there is a limited amount of work available to use to cycle. When you add required work, you lose a margin of safety factor to accomplish the cycle.
There are some examples that perform better with more extraction tension, others do not. There is a delicate balance between bore and porting characteristics with the action system (among other things) that relate to this.

[jackblack73]

That's strange because BCM says right on their website that BCG includes: BCM Extractor Spring, Black Extractor Insert, Mil-Spec Crane O-Ring

It's interesting, in the past it's been pretty well known that BCM BCG's don't come with the o-ring installed. However, I just checked my most recent BCM BCG that's only a couple months old, and the o-ring is installed. I wonder if it's because it came with a 300BLK upper.

[wildcard600]

It's interesting, in the past it's been pretty well known that BCM BCG's don't come with the o-ring installed. However, I just checked my most recent BCM BCG that's only a couple months old, and the o-ring is installed. I wonder if it's because it came with a 300BLK upper.

Of the 5 BCM bcg's I have, three came with the o-ring already installed (free BCG's with purchase of upper) the other two came with the o-ring inside of the bag the bcg was packed in (in a little sealed separate compartment). All were 5.56 uppers that had the o-ring already installed.

I removed the o-rings on the bolts that had them already installed and stuck them in the parts box. Seems to me that its just easier for BCM to include them already installed with bolts that are shipping inside of uppers instead of trying to remember to add a little bag to each shipment.

I think the o-ring is useless if the extractor spring is correct, but I am glad that BCM includes them just in case.