I've been training with my M&P .40 now since March when i purchased it. MRJ are the first 3 letters in the serial #. I'd say 7 out of 10 times upon the last round fired the gun does not go to slide lock. I have a habit of putting slight pressure on the release with my thumb because thats where my grip is. Both right and left handed shooting. But it's the slightest of pressure. I've done a few tests with this grip, shot 2 rounds and slide lock when I'm not putting accidental pressure on the release. However when I'm under the clock and running the stages in comps and training I don't have the time to stop and think about my grip, it's all muscle memory. Besides this adds at least a second to my time to rack the slide after reloading. Other firearms I've trained with don't have this issue. I've checked the mags to see if they aren't engaging the slide lock effeciently when both the slide was off and on. I didn't notice an issue. I also do not load them to capacity. they are 15 round mags usually loaded to 13+1. Any input would be greatly appreciated. Does anyone who has a M&P have similar issues? Any recomendations on changing the mag springs or the slide lock spring? Thank you

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