I had one for my M&P45 and was not all that happy with the fit. I exchanged it for the Blackhawk Serpa and found that better. The only issue I have with that style of holster is that they kinda stick out too far from my side.
Anyway. Try this (Unloaded gun, of course). If you have a hair dryer heat the holster evenly. Take the unloaded gun and put it into a sock. With the holster heated push the gun in the sock into the holster and let it stay in there overnight. I use the procedure (no heat) to loosen my leather holsters when they hold a little too firmly.
Peace.