Today was the 4th time at the range for my Shield 2.0 .40 and I noticed something strange going on with my brass. This could have been going on before but I have started reloading recently so I had reason to inspect the brass more closely and to collect it.

I first notices scratching on the face of the rim. When I field stripped, I noticed very small brass flakes on the slide. The area around the firing pin and extractor had brass scratch marks.

Attached are photos. Keep in mind that these are HD photos so it looks a lot more obvious than you would see with the naked eye.

So what do I have going on here? I shot some reloads and some factory. Most was brass, some was aluminium.

Attached Images

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Have you looked at your magazines to see if perhaps the feed lips have and type of burrs on them?

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I checked. Nothing going on there.

Kinda typical for high pressure cartridges such as the 9mm & 40 in compact pistols. Whats happening is the slide is starting to unlock and drop before the pressure in the barrel has dropped and the FP retracted. Notice the "skid marks on your cartridge heads and the "tadpole" mark on your primers. This is what causes it

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S&W Accumulator

It certainly does look like as you described. So I'm to understand that is is normal?

I noticed the "tadpole" mark. Am I understanding that the shell is dragging across the firing pin, creating the elongated strike mark?

Check your ejector. A small length may have broken off, allowing the shells to get too close to the breech face and scrape against it as they are ejected. The ejector in my Shield 45 protrudes about 5/16 of an inch from the breech face. I don't own a Shield 40, but its ejector is probably similar in length. It should be obvious if it's broken because it likely has a jagged tip.

Regarding the "tadpole" indentations on your primers, those are perfectly normal and will not affect the functioning of your Shield 40 in any way. I have three M&Ps: A 1.0 40/357 compact, a 1.0 Shield 9, and a Shield 45, and they all put "tadpoles" on their primers. They have 29,000 rounds between them and they work perfectly. So at least that's not a problem.

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What, me worry?

Doesn't look unusual to me.

Macro lenses make everything look worse than it really is. I am convinced some of the guns I sold on GunBroker would have sold for more if I had taken fuzzy pictures with a cell phone instead of clear close up pictures that showed every detail. A macro lens can make finely a machined part look like it was carved out with a chain saw.

What you have there are tool marks on the casing from the breechface. Looks normal to me. Brass deposits on the feeding rail on the bottom of the slide are also normal. Brass and aluminum are soft, and the environment there is hostile, to say the least.

If you look closely at the casings and the breechface with a magnifier, you'll find that the marks on all the casings are individually similar, and all have the same characteristics as the vertical toolmarks on the breechface.

If you are concerned about it, send the photos to S&W Customer Service: [email protected]

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Ret. LE, FA Instr, S&W Armorer

What factory ammo? Were they your reloads?

How many rounds had you shot up to the 2nd pic (dirty breech face) and 3rd pic before cleaning it?

Factory Federal, and my reloads. Medium loads. Nothing hot. I would say I had about 300 rounds through it since last cleaning. All photos were after this ~300 rounds.

The scenario described by Mike, SC is very logical. That and the other posts put my mind at ease. I'll let it ride and keep an eye on it.