Problem w/ my M&P 40

[Mark in GA]

Went out Saturday to start working up loads for my M&P 40 and noticed something seemed to be off. The pistol fired and cycled just fine. However when I looked at my fired brass, all of it appeared to have deformed primers. Even with the starting powder charges and mid-level charges. I dropped in some factory rounds and they did the same thing. I went home and began to clean the pistol and look it over and that's when I noticed that the firing pin hole was not machined round nor flat. See the attached pics. I pulled out my M&P 45 for reference it is machined perfectly round and flat.

This can't be right. Should I call S&W? The deformation on the primers matched the deformed shape of the firing pin whole. The first slide is my 40 FS and the 2nd is my 45 FS.

MArk in GA

 

[reloader550]

Mark, the 9mm and 40 cal guns have that tear drop shape cut at the fire pin hole for primer flow back. The standard operating pressures of the 9mm and 40s&w are the same 35,000 psi, the 45acp runs at 21,000 psi, much lower, and less of a chance of primer flow back. Hence the lack of the tear drop shape cut on the 45 breech face. My reloaded 40 ammo cases, and factory loaded ammo cases, look the same. All is good, nothing wrong with your gun or ammo.

 

[Lee in Quartzsite]

If you do a simple search for defaced primers you will find many Threads on the topic. It is NORMAL and a common trademark of all M&P pistols. Just go out and shoot it and have fun

 

[tonesurfer]

Glock puts a nice rectangle pattern around the primers when fired.
S&W puts a tear-drop, because they are sad they aren't as good as a Glock

 

[Laddy Smith]

Rectangle

Glock puts a nice rectangle pattern around the primers when fired.
S&W puts a tear-drop, because they are sad they aren't as good as a Glock

I heard the Glock leave a rectangle shape to match the lines of the gun.....

Lad

 

[growr]

Nothing wrong with your gun....no need to send it back at all. Shoot it and enjoy!

Randy

 

[Mark in GA]

Thanks guys for putting my mind at ease.

Mark in GA

 

[Bigdan69]

My m&p 40 dose the same thing, nothing to worry about there ole buddy