I have been testing loads for my M&Ps this past week. Was thinking of switching to 147s from a 124 (FMJ). Anyway, I loaded some Star 147s with 3.2 grns of Clays. The load felt awesome. Soft, flat. However, it key-holed out of both of my M&Ps. So, I bought a box of Winchester 147s (White Box). They were a little more stout feeling than my handloads and a tad hotter - about 135 PF. They key-holed too. About 3 or 4 of every 10 rounds key-holed at 20 yds. So, I ordered 1000 147s from Atlanta Arms (the Team Glock Load). Wow! These were really soft and very consistent. The chrono'd at 128 PF with on a 6 fps standard deviation. Problem is, when I was testing for accuracy, 2 out of 10 rounds would key-hole at 20 yds. This is happening out of both of my M&Ps. I am stumped. Could it be the length of the barrel not being long enough to stabilize a heavy bullet? Has anyone else had these problems? Any ideas? Thanks.