I just bought two new MK2 magazines from Midway. They both came in the exact same package (marked M-10) , but they are a tad different. One of them has a hole about 1/2 inch from the top that exposes the spring, and a projection up there too. There is another projection on the opposite side (as viewed from the front of the mag). They both will fit in the gun, but the projection hangs up when removing the mag. I have not tried actually shooting with them yet. They both have a different follower button than my old mags. Can anyone shed any light on why the one mag has those projections? Here are some pictures. I hope you can see what I am talking about.