My .300 blk 8" andro upper wont extract without the black o-ring. The brass doesnt exit the reciever and gets jammed up.

Not a big issue, just leave the o-ring and it extracts fine. My other rifles never required the o-ring though, and it seems to cause lots of brass chips in the chamber lugs and bore, and the bolt doesn't go into battery nearly as easily as my .223's . I would like to find a better solution than leaving the o-ring on. Is my extractor spring just weak? Or is this a pressure issue?

There are a lot of pressure issues with the 300 Blackout that cause improper cycling. What is the reason for taking the o-ring out? You're referring to the o-ring on the extractor right?

I presume your AR rifles don't have 8" barrels.

All due to gassing, balance from shorter dwell time and gas port size. The "patches" are  buffer weight, spring tension, and in this case beefing up the extractor. Adjustable gas block is a more custom tweak, which might even entail opening gas port too to be able to shoot all loads, both with or without a  can.

And yes, they make stronger extractor springs. The BCM extractor kit for example comes with both stronger spring and o-ring.

Beefing up the extractor, while essentially a kludge, can be a permanent one. And as you've found, an easy one.

- OS

Thats what I was wondering. I think the extractor is chewing up the brass. Brass chips everywhere and down the bore. Without the extractor o-ring, it doesnt leave chips, but it also wont eject properly. Im looking for a solution that avoids brass shavings and ejection problems. I'll see if I have any stiffer extractor springs around.

Buy a Sheridan case gauge and check your cases/rounds.

Over length cases caused those issues early on for me.  I didn't have my sizing die cranked down far enough.  The trimmer indexed on the shoulder causing cases to be too long.

Read the post above yours as that is good info.  Which weight buffer and what spring are you running?

Adjustable gas block. Thats how I fixed mine.

Standard spring, carbine buffer.