I bought an M&P9 fullsize a little bit ago and have been practicing its manual of arms in my basement with snap caps since I got it. Every time I would insert the mag, no matter how perfectly I slid it home, the slide would not go forward on its own… I have done it dozens of times, and figured it just needed shooting, and it would work itself out. Not that I’d count on it happening as part of a reload drill, but every other M&P I’ve played with at the range would drop when I inserted the mag right.
I took it to MDFI’s carbine I class yesterday and was loading/making ready and put a full mag of live ammo in it for the first time (yeah I brought a brand new gun to a training class - it ended up working fine), and lo and behold, the slide went forward…!
So,
How does the gun know the magazine has live ammo in it???
You just have to hit it at the right angle to do it. The mag does have to have rounds in it though. On my M&P 45 you have to hit the mag in towards the back of the pistol grip lining up with the back strap. I don’t know if it will be the same on the 9. I guess you just have to find that sweet spot.
Macman37 my 1911 does the exact same thing. Load it with snap caps and no slide release. Load it with 8 .45 rounds and it does it. My guess is the added weight of the rounds increases the inertia of that magazine going into the magazine well making it easier for the slide lock to go down.
I don’t believe S&W ever intended for the slide to drop by itself while insertin a loaded mag. That being said mine does it almost every time. Since I use mine for 3-gun as well as CCW and HD I rather like this little quirk of a problem. I have come to expect it but if the slide remains locked when inserting a fresh mag it is no hardship to rack the slide like your normally would.
It’s just physics and how you insert the magazine.
The slide has more mass (inertia) than the polymer frame. Slam the frame with the weight of a loaded magazine, and you will move the frame more than you will move the slide (frame has less inertia and will move sooner) so the frame will bump forward a hair, letting the slide stop break free from the notch in the slide, and the spring then pulls it down out of the way and the slide closes.
Hold your pistol with the barrel pointing to the sky, slide locked back, then hit the rear of the grip (where the disassembly tool sits) with the heel of your palm at a 45 degree angle…it should drop it every time.
All 4 of my M&Ps slides slam home when I do speed reloads or Tac reloads. They have been doing it since day 1. It has to do with speed and how firmly you insert the mag. The only time they don’t do this is when I reload slowly, when not doing drills or if my lady is with me.
Occam’s Razor: your thumb is resting on the slide release as you smack the mag home, with physics and inertia are doing the rest.
DISCLAIMER: it may merely be that my guns are immune to what is otherwise a fairly commonly reported phenomenon with the M&P series.
I’ve tried it with my .45 middy and 9c, and the only time the slide closes “on it’s own” during a slidelock reload is if my thumb is touching the release as the mag is sent home in the well. Keeping my thumb well away, I’ve smacked mags in like the gun owed me money: nothing. Nada. Zip. Give it a try sometime, making absolutely sure your thumb is nowhere near the release vs. putting it on or near the release. You may discover something new about how you grip your pistol.
On March 28, 2010 Mac’s M&P becomes self aware. In a panic, Mac tries to pull the plug…
Lack of pressure from the now loaded magazine’s spring combined with either fortuitous thumb placement or an inertial trick that never happens to me will result in auto-forwarding on the M&P and many other handguns.
Might be the simplest explanation but I’ve experienced and replicated this phenomenon with several different types of guns while deliberately ensuring that my thumb is nowhere near the slide release.
If you hit the baseplate during a reload square at 90 degrees then you need to release the slide, if you insert the mag and hit the baseplate at 45 degrees the slide will go forward on its own.
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