I bought one that would hang up. There was a burr on the rear of the lifter that needed to be removed with a dremel tool. It has fed great the last two years. The problem with rough machining is that occasionally burrs open and catch on stuff. I would hit it with rem-oil spray after removing the stock and cycle it 500 times to see if it improves. Oil as needed but run it a little wet.

__________________
Front sight and squeeze