After rounds sit in my M&P 40c magazine for an extended period of time (months) they come out dented.

Has anyone else seen this? These were brand new 180 grain HST rounds, but this has happend in the past with other loads. Must have something to do with mag spring tension? I don't feel like the spring tension is excessive.

Thoughts? All of the rounds I pull out of the magazine have dents to some degree....these two were the worst.

Attached File

That has never happened in my M&P 40C.


How were the magazines loaded, by hand or with a loader (Uplula, etc) ?

The magazines were loaded by hand (me).

If I load a magazine by hand, then immediately unload it, there will not be any marks on the rounds. This only happens after the magazines sit for an extended period of time. There has to be some force acting on the rounds while they sit in the magazine....

Happens in every magazine?

Good question....I only notice it in the 10 round magazine with the pinky extension. I don't notice it in the other magazine (I only have the two mags that came with the gun).

Spring getting weak allowing the rounds to bounce around?

Those two rounds that you showed.  Where are they in the stack?  Stock springs?  Do you slam the mags in hard?  I'm not limited to 10 rounds, so I don't know what the internals look like in your mag.  Is there a spacer block?

Middle of the mag. Standard mag, stock springs. I don't slam the mag at all. This happens over the course of time where the rounds just sit in a loaded mag that sits in the pistol.

No, this pistol isn't a heavily shot pistol. The mag springs are still stiff.

I just bought a couple more mags online.

Just with HST or other manufacturers?  I've seen this also in one of my guns, but in .45.   Damn, which one is it.  Can you chamber drop the round?  Is the bullet resting on the edge of the barrel  ramp when the slide is closed?

Happens with other manufacturers. This happens to the rounds that just sit in a loaded magazine- not to rounds that have been chambered.

Hard to tell from the pictures, but the dent is above the base of the bullet. Strange....

IIRC the dent is at the base of the bullet.  Bullets will rotate as they are inserted into the mag and travel down.  Double stack mags taper to one feed row.  Three to four rounds down is where the bullets are crossed over each other and point not up, but down in the double stack.  I wonder if spring tension and the mag body are contributing to this.  I just checked my 9mm guns and saw the similar bullet swag from the casing.  This is from Speer GD in 115 gr +P+ in several different G19 mags.   Also with HST in 9mm 124 gr +P.  I'll look later for the .45.  Also nickel cases.  

Is there indentations in the sides of the 10 rounders?  What keeps you from loading a 11th round in the mag?

You can see this from a ETS brand clear mag to see what I'm talking about.

Can you chamber those two rounds without issue?

I'm having trouble picturing what you're saying, but I'll look at pictures of some clear mags.

These rounds WILL load and fire without issue. I really like the M&P 40C and my version has been 100% reliable. This is just a quirk I found with my sample.