I have a 40 and 40c. I have had the full size for 6 months and the compact for two weeks. The full size started doing this about a month ago. I have around 1200+ rounds through it. The compact does not do it but I only have 250 rounds through it so far. I do not slam the magazine but I do close it with some force. It doesn't really bother me other than in a high stress situation the more repetative the your actions are the less likely you will have trouble.