I was at the range today & was having an issue w/ my magazine that I wanted to run by everyone:
It's a 12-round magazine for my M&P9c. For the first few go-arounds I would load it w/ 5 rounds & cycle through it & 2 other magazines I had. Then I started to load all 3 w/ 10-12 rounds. I load the ammo into the magazines w/ 9mm Glock mag loader. On almost every cycle where the one particular mag had 10-12 rounds it was ALWAYS jamming up w/ exactly 5 rounds left. The remaining 5 rounds in the mag would come tumbling out & I'd have to stick a pen down the magazine to get the spring to rise back up to the top.
Upon getting home I opened the magazine up & there doesn't appear to be any obvious obstructions, though there is a little bit of grime along parts of the spring.
Any ideas what could've been causing the magazine to consistently lock up at the 5-round mark? Anything I should be looking out for or doing when I clean it?
Thanks in advance.