Ive got an M&P Vtac 9mm that Ive had for about a month now. I noticed an issue yesterday at an IDPA match that kinda irked me. Ive gotten used to the slide returning to battery automatically with a new mag inserted, worked fine for a month for me with full mags. Fast forward to yesterday. Downloading to 10 rnds and it gives me fits many times it would not catch a round and a couple other times it stood the round up vertical, causing a jam. Anyone got a fix for the slide auto forward? Towards the end of the match I would just keep my thumb on the slide stop to keep it from disengaging, and that solved my problem. Thats just one more thing to have to think about during a reload, and I would rather not have to. The gun has about 500rnds through it, and it happens with all three mags that I have.

I don't have a solution, but I've also noticed this problem (especially the inconsistency of it). I have one M&P with over 1500 rounds, and it doesn't do it any more. I hope as my others increase in round count, that they too do away with this problem.

Its consistent with a full mag, It works every time. Its just with the downloaded mag for IDPA that causes me problems.

It's not a feature or a problem with your gun, hence there is no solution. It's an effect that sometimes happens.

Page 16 of the M&P Pistol owner's manual:

WARNING: DO NOT USE EXCESSIVE UPWARD FORCE
WHEN INSERTING A LOADED MAGAZINE INTO THE
PISTOL. EXCESSIVE UPWARD FORCE COULD CAUSE
THE SLIDE TO MOVE FORWARD, CHAMBERING A ROUND AND
MAKING THE PISTOL READY TO FIRE.

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M&P40c/15-22/SD9VE/Mossy500

It doesnt even take excessive force, just a good solid mag insertion will do it.

It's just physics.

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M&P40c/15-22/SD9VE/Mossy500

None of my 1911s have ever done it, none of my glocks have ever done it.

Years ago I read an explanation for why Glocks would go into battery during a reload on the Glockmeister website.

I forget the physics of it now, but the bottom line was it could do it if the muzzle was pointed upward, but not downward.

I know it's done it to me numerous times and yes the muzzle was pointed upward. If you look at the grip angle it would be awkward to put a magazine in the pistol with the muzzle pointed downward, so I can't say I've ever remembered it happening with the muzzle pointed down.

I know it's done it with my Glocks and some of my 1911's.

I've never relied on it happening 100% of the time; I always expect that I'll have to grip and pull the back of the slide to chamber a round. If it does happen during a reload, I just roll with it, if not, I'm ready to do it myself.

Bill

As Jyezahn said, it's neither a feature nor a problem. It just happens.

It has to do with the force of magazine insertion. If you slam the mag in, this could cause a round to come out prematurely. That is probably why you're seeing a type 1 malfunction. The solution to that is to use less force.

I don't know the IDPA rules. Are you required to use 10 rounds or less per mag? If that's the case, it would be to your benefit to buy a few 10 round mags. Both my .45 and .40 will release the slide on a full mag, but I only have 10 round mags. I've never had it happen on any other gun than an M&P.

A note on slamming mags in. If the slide is closed, as in a tactical reload, too much force can be bad. If too much force is used, the top round can be dented by the bottom of the chamber. This could cause a feeding malfunction. So, the goal is a firm insertion, not a slam.

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Freedom isn't free.

At LE requal we call this syndrome "the Mongo reload." Our duty HK's will drop the slide on a reload if the magazine in inserted extra smartly. Many auto pistols will, including our M&P's. Some competitive types use the Mongo deliberately to get speedy emergency reloads. But Murphy's Law being what it is, when you really want the Mongo to work, it won't, leaving you wasting precious time on a tap rack bang that might have been avoided by a more disciplined manual of arms.

If you get an unwanted slide drop, check your mag & slide stop springs. If they are fresh, you might just have to chalk it up to the stress of timed fire making your reloads a tad too forceful. It happens to all of us eventually.

My old Glock 19 did it. To the OP, older M&Ps had a tendency to do this, none of my 4 M&Ps do this (maybe I don't "slam" the magazine hard enough, IDK). Perhaps you could try putting a the newest generation slide stop in your gun, see if that doesn't fix it for you. It's cheap enough to where it's worth spending the money on the slide stop.

that worked. the gunshop I bought it from put a new slide stop in and their armorer tweaked the spring a bit and now it doesnt close under normal mag changes.

Glad to hear it!