M&P 9mm Reload with Chambered Round, Gun goes out of Battery

[ddraper]

I had two instances of a problem yesterday that is bothering me. Full size M&P 9mm.

I shot the IDPA Classifier yesterday. Which for those familiar with it know that stage 3 calls for 2 tactical reloads. Basically the gun has a round chambered and is in battery. You drop and store the mag and replace it with another one (that theoretically has more rounds than the one removed).

Guns is loaded with 10 rounds and then one round chambered. 6 shots taken. Drop mag and store, replace with anther mag loaded to 10. Go to shoot and no striker fire, cycle slide, ejecting live round, and then gun is fine and fires.

This exact same scenario happened to me twice yesterday. All I can figure is when I inserted the full magazine it somehow knocked the gun out of battery. I tend to kind of slam in the magazines for two reasons. First I want to ensure the magazine is an and seated the first time and second, when performing a slide lock reload I want the slide to disengage, move forward and chamber a round without me having to do it.

Any thoughts on what might have happened?

 

[StefanoMapo]

I had two instances of a problem yesterday that is bothering me. Full size M&P 9mm.

I shot the IDPA Classifier yesterday. Which for those familiar with it know that stage 3 calls for 2 tactical reloads. Basically the gun has a round chambered and is in battery. You drop and store the mag and replace it with another one (that theoretically has more rounds than the one removed).

Guns is loaded with 10 rounds and then one round chambered. 6 shots taken. Drop mag and store, replace with anther mag loaded to 10. Go to shoot and no striker fire, cycle slide, ejecting live round, and then gun is fine and fires.

This exact same scenario happened to me twice yesterday. All I can figure is when I inserted the full magazine it somehow knocked the gun out of battery. I tend to kind of slam in the magazines for two reasons. First I want to ensure the magazine is an and seated the first time and second, when performing a slide lock reload I want the slide to disengage, move forward and chamber a round without me having to do it.

Any thoughts on what might have happened?

your M&P has the magazine safety?

 

[Saudade]

Can you push the slide forward with your thumb (not racking it) and have it fire?

 

[Rastoff]

Interesting problem. I've never heard of it before. However, I don't think the slide is going out of battery.

I wonder if the trigger bar is being knocked to the right?

 

[ddraper]

No magazine safety. Magazines are un-modified. No cut followers, no loop removed from the magazine spring.

I didn't even try pushing the slide forward. SOP for me in IDPA for this type of malfunction is rack and go.

I am going to disassemble the gun and take a look. I will check out the trigger bar. One thing that does not make sense to me is during the load and make ready there is a chambered round and load a magazine. That is similar to a tac reload and I never ran into the problem.

I am going to load up 20 or so dummy rounds and see if I can reproduce the problem.

 

[OKFC05]

http://smith-wessonforum.com/smith-...5080-m-p-pro-fails-fire-after-mag-change.html

 

[ddraper]

http://smith-wessonforum.com/smith-...5080-m-p-pro-fails-fire-after-mag-change.html

Sorry about the dupe. I didn't see that thread. Problems sounds the same.

I will look everything over as I also installed an Apex in mine but that was 5+ months and 1800 rounds ago.

 

[TacticalReload]

There is a thread on this at brianenos.com. Apparently inserting a loaded magazine with a stiff mag spring can cause this to happen.

Are you using 10 round mags? Are the mags newer? How long since your last recoil spring change?

 

[ddraper]

There is a thread on this at brianenos.com. Apparently inserting a loaded magazine with a stiff mag spring can cause this to happen.

Are you using 10 round mags? Are the mags newer? How long since your last recoil spring change?

10 round mags, loaded with 10. Mags are not even close to new. They are all just shy of year old with about 4k rounds through them collectively.

Recoil spring is stock, never changed. Same age as mags. 11 months with about 4k rounds on it.

I was trying to reproduce the problem this morning using snap caps but I don't have 11 of them so there was 1 snap cap in the chamber but only 4 in the magazine. Going to load some dummy rounds and try with 10 in the magazine.

 

[TacticalReload]

The guy on the other forum was specifically having issues with the 10 round mags. He solved the problem by clipping two coils off the springs, which wasn't an issue since the 10 round mags apparently use the same springs as the 17 rounders despite having a shorter effective mag body. YMMV. I would also swap out the recoil spring for a new one since that's what holds the slide closed.

 

[Bonephish]

I would also swap out the recoil spring for a new one since that's what holds the slide closed.

This is most likely the problem^^^