M&P9 Fullsize FTF Malfunction

[C4IGrant]

@subzero

I remember this happening occasionally with my older mags with black followers. I got the newer followers from S&W and it hasn’t happened since.

If you do have the newer grey follower, I would think it might be time for a new mag spring.

Could be. The new followers are marked with a number “9” on them. If the springs are worn out, the rounds could retract into the mag easier (causing this issue).

C4

[C4IGrant]

@larry0071

Dumb question - Me and a few fellows were doing some repetitions with 1 round in a mag (shoot at target) followed by a emergency reload with a mag with 2 rounds in the mag. Both of us had MP pistols, his a MP9 and mine a MP9C, and we both realized that during an emergency reload (fast as you can while under control and being scrutinized by Gut_Shot_John) that both of our MP pistols would drop the slide with a fast and firm insertion. This is not to say that we were “slamming” the mags into the pistols, but we were aggressively inserting them with some amount of speed and force as we were doing our best (low skill level limited) to facilitate an emergency mag change during a bad-guy encounter.

The dumb question - Is this slide lock designed as such that it is intended to release the slide upon a firm/fast insertion of the magazine, or is this a design flaw that is being recognized? I also own a very old Glock 17 and have never seen this happen, so it is something new to me. Also of note is that both of these MP pistols are recently new purchases, and I know mine has the grey follower in them, but I do not know if the ramp or the number 9 is in it. I will need to look for that.

Did S&W SPECIFICALLY design this to happen in their guns? No, they did not.

C4

[5pins]

@C4IGrant

This does not fix it and actually aids in the auto-forwarding issue.

C4

That’s right. The spring holds it down not up.

[TY44934]

Probably obvious, but is the interior of each magazine clean? My rule of thumb is: mag comes apart for cleaning every time it hits the dirt.

[subzero]

@C4IGrant

During our testing, we found that sometimes the round would NOT feed correctly during auto-forwarding. From what we could figure out, this was due to the angle in which the mag was inserted. So if you come straight in (level and even with the mag well), the gun would auto forward, but chamber a round. If you came at a more forward angle (thusly striking more of the rear of the grip), there was a much greater chance the round would not feed.

The theory for this is that the energy coming from the back of the gun is causing the bullet to nose dive and retreat into the mag as the slide is coming forward.

I wonder if it isn’t that the mag catch isn’t a little worn or has a burr, and is holding the mags just a touch low.

I’m looking at one of my 9s with the slide off and the barrel in place, and the only way I can see for this particular malfunction to take place is for the slide to start going forward prior to the mag being seated, stripping the top round off a millisecond too early. That is, assuming the followers and springs are all good (which we are).

I hate to ask because I’m sure it is, but are you sure this problem is an auto forward problem? If you slow down your reload just a touch at the insert and make sure that it’s your action that’s dropping the slide after the mag clicks, does this happen? I’ve found that it’s REALLY easy (due to my thumb placement and the ergos of the pistol) to drop the slide on my M&P, so much so that I was trickfucking myself into dropping the slide on an empty chamber a few times.

I can easily believe you can’t replicate the malf with ball ammo. Ball almost points into the chamber just sitting in the mag. I halfway believe this gun doesn’t even need a feedramp for ball ammo. The slightly different taper and nose shape of JHPs need a little direction though.

[C4IGrant]

@subzero

I wonder if it isn’t that the mag catch isn’t a little worn or has a burr, and is holding the mags just a touch low.

Doubt it. I have at least 5 new M&P’s and they all do the same things (to a certain degree).

I’m looking at one of my 9s with the slide off and the barrel in place, and the only way I can see for this particular malfunction to take place is for the slide to start going forward prior to the mag being seated, stripping the top round off a millisecond too early. That is, assuming the followers and springs are all good (which we are).

Yes. There is where the improper mag insertion happens. The shooter actually makes contact with the frame (causing it to release) before the mag is fully seated in the gun.

I hate to ask because I’m sure it is, but are you sure this problem is an auto forward problem? If you slow down your reload just a touch at the insert and make sure that it’s your action that’s dropping the slide after the mag clicks, does this happen? I’ve found that it’s REALLY easy (due to my thumb placement and the ergos of the pistol) to drop the slide on my M&P, so much so that I was trickfucking myself into dropping the slide on an empty chamber a few times.

What you are describing is a problem, but we keep our thumb out of play for testing.

I can easily believe you can’t replicate the malf with ball ammo. Ball almost points into the chamber just sitting in the mag. I halfway believe this gun doesn’t even need a feedramp for ball ammo. The slightly different taper and nose shape of JHPs need a little direction though.

When we created the FTF, we always did it with JHP’s.

C4

[nickdrak]

Just an update…

My brand-new (manufactured Jan/2010) M&P9 fullsize (LE SKU#309301) that I picked up two weeks ago does the same thing when I tried to “Slam-Charge” load it with my duty Win Ranger 124gr +p ammo.

I still love these guns, and I have trained myself not to purposely try to “Slam-Charge” my pistols during speed reloads, and rely on the “Power-Stroke” method exclusively.