Poor extraction, when shooting suppressed I have to clean the chamber good after 70-100 rounds or I start having issues.
Buffer weight won't matter if the extension tube depth allows the carrier to travel far enough to strike the tube or receiver. My Aero buffer kit allowed the carrier to strike my receiver just in front of the tube. I cut a small notch in the tube for the detent so I could get one more revolution inward with the extension and still had to add a couple quarters in the bottom of the tube so the carrier would not have so much forward travel before hitting the bolt catch, about 3/16 inch is where I ended up. You want that bumper on the buffer to hit the bottom of the tube before the carrier can hit the front of the tube or receiver.