300 Blackout cycling issue

[smustian]

Check your bcg and see if there is an o-ring under the extractor. If so, remove it. An o-ring can cause the extractor to hang onto the case rim tighter and longer.

[dellet]

Hello all and thanks in advance for any help.

I built a 300 blackout upper and am using it on my Stag Arms lower 5.56/.223

I’m having trouble tuning my gas block to where it’ll cycle properly (lock the bolt back) and getting the shell to not hit the shell deflector.

Should I consider changing my buffer spring?

I’m thinking of trying this spring- http://www.davidtubb.com/ar15-buffer-spring-stainless

Parts list:
Anderson Manufacturing AR-15 Stripped Upper Receiver
APF Armory Bolt Carrier Group AR-15 223 Remington, 5.56x45mm Nickel Boron
Nitromet Carbine Gas Tube
JP Enterprises Low Profile Adjustable Gas Block - .750 - Clamp Style
16” stainless steal barrel 1:8 twist

Looks like going to an M-16, heavier carrier would help.

You mention a piston operated system, but have a carbine length tube, so there is some confusion. Can you add a link to the piston so we can see the specs?

Your buffer should be marked, probably H then a number. That would be good to know.

Finally, if the bolt locks back and you are trying to get the brass to stop hitting the deflector the Tubbs spring is the wrong thing to try. All that will happen it make the brass hit the deflector harder.

But really it sound like it is basically operating as designed.