This is usually due to a rough surface on the "feeding rail, or "disconnector rail" on the bottom of the slide. The top round in the magazine, the one under the feeding round that ends up on the floor, gets "dragged" forward by the slide during the closing (feeding) sequence. As a result of being moved forward the round is extended slightly forward out of the magazine tube, and catches on the frame when the magazine is removed.
A little bit of careful, light polishing along the lower flat of the rail, and some light lubricant, or moly on the location will usually take care of the problem. Some of the slides have a very rough surface at the flat area indicated in the photos, including machine marks. See attached photos for the location to lightly polish.......
Ret LE, FA Instr, S&W Armorer
Last edited by armorer951; 03-13-2017 at 10:06 PM.