BCM BCG came with an O ring...where does it go?

[Leaky Waders]

Hi,

So I ordered a BCM upper so I can have a scoped AR and a Iron Sighted AR by just swapping uppers.

The BCM bolt carrier group came with an oring...where does it go? Is it a spare or does it need applied before being fired?

Pics of the new upper and old upper below.

 

[Zerodefect]

Probally a spare oring. It goes around the extractor spring. It helps give the extrator more bite to pull the caseings out of a carbine.

If you BCG came assembled, I'd assume its a spare.

 

[Gary G23]

The BCM does not come with an O ring around the extractor spring. However, unless you have a carbine length gas system I would not put it in.

 

[briansmithwins]

I've got BCM extractor upgrade kits in both the 16" middly and 20" rifle, with the o-ring.

It doesn't seem like you can have too much extraction force with the AR.

BSW

 

[Gary G23]

My experience was different than briansmithwins. When I installed the BCM kit in my 16" middy it turned a previously 100% reliable gun into a jam-o-matic.

 

[Zerodefect]

Says right on their website that the oring is for sbr's. May not be needed.

http://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm extractor spring 3pack.htm

Works fine for me.

 

[mp5a3]

I use it in a 20" without issue