Those Mysterious Slide Dimples

[sandog]

So whenever I clean one of my M&Ps, I see these dimples put into the inside of the slides. The ones on my .45 Shield make a "C" pattern with a deep dimple, and the ones on my full-size 9mm have 3 toward the breech that are deep, and 6 towards the muzzle end that are shallower, 5 in a line and one next to the row of 5.

I've been speculating as to their meaning, anybody have any clues as to their purpose ?
Line assembly workers ID code, date of manufacture stamp, Alien crop circles ?
My PC Shield is my bedside piece, always loaded, so I can't remember if it has them too. Next time I have it apart I'll have to check to see if it has dimples on it as well.

The other thing I am wondering about is the semi-circular cuts in the bottom of the .45 Shield slide. They look too concentric to be bad machining or a slip of a tool, my other Shields don't have it.
When you rack the slide, it makes a faint clicking sound, like when you tighten up a zip-tie.
The .45 functions great, but I am mystified why these are there.

[mckenney99]

The dimples are a mystery to me also, but I don't lose any sleep over them either. The scallops machined into the center pickup rail are there by design and on the 45acp Shields only. If I remember correctly they are there to help slow down the slide velocity as the rail interacts with the top round in the magazine.

[swsig]

There are some old threads about both of these questions. The dimples are S&W code that indicate which machine the slide was milled on. The semi-circular cuts are designed to gently grab the top round in the magazine and pull it to the back. There is precious little room in the mag well, and if a round is too far forward, a failure to feed jam can result. Thus the cuts reduce the chance of a misfeed if a round is not seated properly. One early purchaser of a Shield 45 wrote to the Forum complaining about these cuts, stating that they were an example of poor quality control, and that he was going to grind them off. Some of us tried to dissuade him from doing that by explaining what they were for, but he ground them off anyway. We wondered if he began to have misfeeds, but we never heard from him again.

[sandog]

Thamks, swsig. I figured the dimples were some sort of manufacturing code, but had never seen any discussion on it.

I had another .45 Shield around 2016-2017 and didn't remember those scallops on the center rail, didn't remember the clicking sound when the pistol was racked either. Maybe it's something S&W didn't start doing from the get go when the .45 was introduced.

I haven't been losing any sleep over those features, but was curious as to the purpose. Thanks for the clarification.

[jamppp]

Some Beretta's have dimples in the slides and in that case they are where a 'hardness test' was done on the metal.

[Jessie]

It’s not for the blind?

[sandog]

They do kinda look like braille !

[Texas40]

Originally Posted by sandog

Thamks, swsig. I figured the dimples were some sort of manufacturing code, but had never seen any discussion on it.

I had another .45 Shield around 2016-2017 and didn't remember those scallops on the center rail, didn't remember the clicking sound when the pistol was racked either. Maybe it's something S&W didn't start doing from the get go when the .45 was introduced.

I haven't been losing any sleep over those features, but was curious as to the purpose. Thanks for the clarification.

Purchased mine as soon as one was available in my area of TX. So its an early first release unit has both.
Never even bothered me and gun shoots great always has.



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[pakettle]

Originally Posted by Texas40

Purchased mine as soon as one was available in my area of TX. So its an early first release unit has both.
Never even bothered me and gun shoots great always has.



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After heat treat, comes hardness check!

[Texas40]

Originally Posted by pakettle

After heat treat, comes hardness check!

Really
Who knew.
I posted the photo to show that early models had them that is all.
I know why they are there.
However having been around mfg and seen many heat treat test dimples I must say they are quite large for that.

Usually a rockwell hardness tester makes little and in some cases hard to detect dimples.




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[Jim Watson]

I think I see tool marks, like it had been kissed by a center drill.

[CH4]

Hmmm
Very mysterious. Like crop circles, but for guns.

[ken158]

Originally Posted by swsig

There are some old threads about both of these questions. The dimples are S&W code that indicate which machine the slide was milled on. The semi-circular cuts are designed to gently grab the top round in the magazine and pull it to the back. There is precious little room in the mag well, and if a round is too far forward, a failure to feed jam can result. Thus the cuts reduce the chance of a misfeed if a round is not seated properly. One early purchaser of a Shield 45 wrote to the Forum complaining about these cuts, stating that they were an example of poor quality control, and that he was going to grind them off. Some of us tried to dissuade him from doing that by explaining what they were for, but he ground them off anyway. We wondered if he began to have misfeeds, but we never heard from him again.

It never ceases that some people think they can out engineer the engineers...