Issue with my M&P40?

[MilesVeritatis]

I just picked up my M&P40 a couple of months ago, and I love the gun, shoots accurately, recoils light for a .40, feels great in hand, but I've noticed it behaving a little funny.

My hollowpoints keep getting compacted. What I mean is, when carrying the gun, the round on top of the magazine that gets cycled into the chamber when I holster the gun and replaced in the top of the mag when I lock it up, after a couple weeks, ends up getting pushed down into the casing until the bullet is half covered by the casing or worse.

I'm not sure if this is an issue with the gun or the ammo, I'm guessing the former, as the ammo is Hornady Custom 155 grain XTP's.

Has anyone else had an issue like this? I'm wondering if the gun isn't quite headspaced properly.

Only other thing I can think of is that the action of being cycled is causing the feed ramp to push the bullet into the cartridge, and that would indicate an ammo issue before a weapon issue.

[LorenzoS]

the round ... ends up getting pushed down into the casing until the bullet is half covered by the casing or worse.

Is this happening after chambering the round once, or after rechambering the same round multiple times?

[kmrtnsn]

We shoot 155gr in our SIGs and HKs, I've never seen what you describe, however, we do have a policy to NEVER rechamber rounds. Why are you loading and unloading the weapon, repeatedly?

[MilesVeritatis]

It happens after the round has been rechambered a few times. I leave the magazine loaded, but the chamber empty when I lock the gun up at night, when I leave the house, I rack the first one into the chamber. I've previously had an XDm and Glock 17 in 9mm and switched calibers when I switched to the M&P as my carry gun, never had a similar issue before, so I was just curious what the specific cause may be.

The solution may just be changing my handgun practices, though my current solution seems the simplest and safest. My M590A1 is my HD gun, but maybe I ought to just start leaving one chambered and putting the pistol in my night stand. No small children, no worries.

[BCmJUnKie]

I ought to just start leaving one chambered and putting the pistol in my night stand. No small children, no worries.

Why do you lock it up and unchamber it at night

Just leave it alone, stop chamber/unchambering rounds would be the first thing

[Nephrology]

You are chambering the same round too many times. This is not the gun's fault.

Load your weapon and keep it loaded. Lock it up some where VERY secure when it is not on your person. Otherwise keep it on your person as often as you can to prevent unwanted access.

This is the best solution to your problem. Buy a second identical M&P40 if you want to dry fire it, you should have a duplicate anyway eventually. A m&P40C might not be a bad compromise.

If you must unload, do not rechamber the same round immediately. put it in the bottom of the magazine. My rule of thumb is no round is allowed to be chambered more than 3 times. On the 3rd time, I shoot it at the range if I want to unload it.

All guns will produce setback eventually. Discard your set back hollowpoints unless you want to blow up your M&P.

[TriumphRat675]

Only other thing I can think of is that the action of being cycled is causing the feed ramp to push the bullet into the cartridge, and that would indicate an ammo issue before a weapon issue.

This is basically what is happening and is normal when you re-chamber the same round way, way, way too often.

DO NOT SHOOT THOSE CARTRIDGES.

If you shoot a cartridge with the bullet set back into the case like you have described, the round will be dangerously over-pressured and your gun will blow the hell up. This situation is a KaBoom waiting to happen.

Stop loading and unloading your weapon unless absolutely necessary and do not rechamber the same cartridge more than twice. I mark the head of the round with a blue sharpie - one tick for the first chamber, two ticks for two chamberings, then shoot or discard it.

ETA: should have read Nephrology's post; that covered it.

[Nephrology]

This is basically what is happening and is normal when you re-chamber the same round way, way, way too often.

DO NOT SHOOT THOSE CARTRIDGES.

If you shoot a cartridge with the bullet set back into the case like you have described, the round will be dangerously over-pressured and your gun will blow the hell up. This situation is a KaBoom waiting to happen.

Stop loading and unloading your weapon unless absolutely necessary and do not rechamber the same cartridge more than twice. I mark the head of the round with a blue sharpie - one tick for the first chamber, two ticks for two chamberings, then shoot or discard it.

ETA: should have read Nephrology's post; that covered it.

That's fine, some advice is worth hearing twice! When it comes to set back handgun ammo, maybe even 3 times is a good idea!

[MilesVeritatis]

Gotcha, thanks for the advice. My solution is just to leave it chambered and put it in my night stand drawer.

I don't exactly have any other "gunny" family members, so I'm having to find this stuff out myself. All the mechanical, maintenance, and legal stuff is easy, some of the practical stuff like this I guess just comes with experience. I did have the common sense to throw out the setback rounds though.

Even though I normally just lurk, over the past few years you guys have helped me out more than you know. Thanks for the tips!

[TriumphRat675]

You are smart to ask, not dumb for not knowing. Welcome to....well, participating in the forum, and thanks for showing up with an open mind.

I was in the exact same position as you a few years back. I've learned a lot from this place, as you did.

After spending time at the local range recently, I'm glad there are some (few) shooters out there like you who are genuinely interested enough to find a good info source and ask, 'cause there are way, way too many who don't.