I carry my M&P40c every minute that I'm not on duty and noticed something odd about the ammo I carry (federal HST 180grain). While looking a the rounds I noticed an indentation around the brass. Basically a ring around the shell approx 1/8" from rim. Usually right about at the point where the bullet stops inside the brass...I asked somebody at my pistol club if they've ever seen it and he said it was common with 40's? I carry a G22 on duty and have never seen this on the ammo. I'm wondering if anyone out there has seen this or had it happen to them, if it could cause any probs, etc. I do unload the M&P whenever I'm not carrying it, could this problem occur from repeatedly chambering a round...I do rotate the rounds fairly often. I've attatched a pic, it's not the best but gets the point across....THANKS

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A lot of my brass has those dents also.

I don't know what it is.

Might be an indentation caused by feeding rounds into the magazine. Or possibly from recoil.

My M&P 357c does not have the indentations. However, when I change the barrel to 40 and put 40 rounds in the same magazines I have the exact same problem. Never had any problems with the ammo or anything else its just an indentation. I have been told by a local gun dealer that is very reliable and knowledgeable about S&W M&P's that it is due to the magazines being tight out of the box.

My rounds look like that right out of the box!

That picture is so out of focus it looks like a 357 sig.

It is the ammo I have used nothing but Hornady Critical Defense loads in all of my carry weapons and never noticed a mark or a dent as you call it. try using those.

Crimp, maybe ?

No thats actually how the rounds look. They have an indented ring around where the shoulder of the case would be if it were a 357 sig.

The picture is not very clear. Is it a ring 360 degrees around the case where the bullet base is? Some auto ammo is crimped in the area of the bullet base to keep the bullet from sitting back into the case during the violence of the firing cycle. Does the round look like this when new in the box or does it appear only after you load the round into the chamber? If the latter, I would say you have a serious problem and should contact S&W.

It's been mentioned on another M&P forum. First post I see about it was posted on 12/2008. Several have stated they have shot the creased ammo without any problems.

I think its lust the way federal ammo is made. My Federal 9mm ammo is crimped and so was a box of Federal 357's I had.

I have fired about 40-50 rounds of the most seriously indented without a problem. It's still a mystery to me. I was told by somebody that it's common with .40 s&w. However, I carry a Glock 22 as my duty weapon, with same Federal HST ammo and haven't seen it with that gun. Nor, has anyone else in the department. I guess as long as it's purely cosmetic and doesn't compromise reliability no real issue. But it still kinda bugs me. Thanks for the replies/input!

I have the same issues with the federal HST ammo..I used some cheap range loads and never had an indentation on any of the casings. I was wondering if anyone else had any issues with other ammo?

I noticed it on all my reloads and on factory ammo, not sure but I would say the nature of the beast. 1500 rounds of both factory and reloads and not one hic-cup
Cracker

Second the crimp diagnosis.

To revive an elderly thread, I had this problem and came across this thread. My ammo was Federal HST, brand new. Looked fine going into magazine, same creases coming out.

I switched ammo and no more creases. This is weird, because I hear nothing but good things about HST. I switched to Hornady Critical Defense. Hope this helps someone...

I agree I had Federal rounds that look that way, but also carry my 40c and use Winchester PDX. The PDXs don't start off looking like that, and after a week or still doesn't. Also noticed that I can go at least 2 weeks before any noticeable set back. Thats a lot better than I was getting with Hornady.

I have the m&p 40c and I have it loaded with winchester pdx1 and I have the same crimps but they do not go all of the way around the bullet. it looks to me like it is in the exact spot where you push one round into the next when loading the magazine. I believe this happens because the spring is tight, once it loosens up there shouldnt be a problem anymore. I have never had any trouble shooting any of the crimped rounds.