Sometime back I picked up a police trade in S&W M&P45. I hadn't really played with it much. I field stripped it to clean it today and took note of these dimples on the underside of the slide. Are these on all M&P's? Purpose?

I have a friend who had a revolver sent back to S&W for warranty work and it returned with two small dimples in the frame. Same thing?

My Shield has them too but they are in a different configuration.

Looks like some sort of braile-like code which could be used durin manufacturing for any number of things indicating the batch or which model it belongs to. They seem a bit too regular in spacing and depth to be for weight or balance.

They are there to identify which CNC machine milled the slide.

If there is a problem with the slide, they can trace it back to that machine.

I use mine to hold grease.

3

It's a fairly new process thats used by the factory to identify the firearm, I know Glock is also doing something along the same line with the Gen 4 models.