Silly as it sounds, this is actually a legitimate question, sort of....

Some semi's work better with one less round in the magazine that specified, at least until the magazine spring gets a little "used".... So, if you have a seven round magazine, loading the top round into the chamber and NOT putting another round in to top off the magazine may be a good idea for a month or so....

(I expect the guns that don't like a full magazine are/were in the same boat.)

I had to learn about everything the hard way. With a lot of help here on the forums. Dad was in the CCC program before WWII, and a Medic all through the war, and while he never got overseas, he likely qualified with about everything that a single Infantryman would be likely to carry, but when I started talking about bringing a gun into the house, he insisted that I bring a badge, too. So I did.... ("Rent-a-cop".) Never could get him interested in going to the range, though.

I had an uncle who was a pistol instructor during WWII, too, but he never wanted to be around 'em after the war. Another uncle briefly ran a supply warehouse in Italy, and could have sent his six kids through college with a handful of the captured drillings & such in there, but when his turn to come home showed up, he handed the keys to the next guy and got on the boat....

OTOH, I'm a born tinkerer anyway, and one of the great things about the M&P's (and the 1911) is that you can pretty easily figure out how they work, and do whatever's necessary.

Regards,

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Stu.