The brass in the face is not an extraction problem it is an ejection problem. The ejector is very short on the M's. If the next round in the magazine shifts slightly forward it clears the slide and pops up into the brass before it reaches the ejector causing it to eject upward instead of to the right. The reason the problem goes away after a few hundred rounds is the mag springs weaken and the slide smooths out causing it to move faster. If the ejector was 1/6" to 1/8" longer it would completely cure the problem.