So I should have put this in the first post, I'm thinking of more stuff that I could've added.
Something to try if you start changing to heavier buffers....
Remember that if you put a heavier buffer in you'll be making it harder for the bolt carrier group to move to the rear. You can make it so heavy that the BCG won't move far enough back to eject the empty brass and / or pick up another round from the mag.
If everything is running fine with your new buffer be sure to also make sure the BCG will lock back on an empty magazine. That'll make sure that the BCG is getting enough gas to move as far back as it needs to. Just load one round and fire it and see if the BCG locks back.
If you use different kinds of magazines, try them all. And try it with the different ammo that you regularly shoot. Generally, if it'll lock back with the weakest ammo (that's generating the least amount of gas pressure) you shoot it'll be fine with everything else too.
