I think the mag springs are playing a role in this problem. In my 9 Shield I've never had to slam a mag home as hard in any other gun, but you sure have to with the Shield. That along with frame flex could be an issue for some of the .40's. The frame could be more dense on some, less in others as well. Everyone should try this test, as I noticed it today. Load in a loaded 7/6 rd mag into your unchamberd Shield, grip firmly then release the mag & see if it feels kind of relieved to let it out. I felt that feeling today & it made me think about the mag drop issue. Don't know if it means anything, but I wanted to pass it along.