Why the Ridges on the underside of the slide? - MP-Pistol Forum

Why the Ridges on the underside of the slide?

This is a discussion on Why the Ridges on the underside of the slide? within the MP SHIELD Pistols forums, part of the Smith & Wesson MP Forum category; Wondering why S&W put the machined ridges on the underside of the slide. Different from the 9mm and .40, and feels like crap when you ...


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Old January 2nd, 2017, 05:16 PM   #1
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Question Why the Ridges on the underside of the slide?

Wondering why S&W put the machined ridges on the underside of the slide. Different from the 9mm and .40, and feels like crap when you pull back the slide if you have a full mag in. Attached a picture of the brass buildup on the ridges i'm talking about. This really seems like a poor addition and would like to machine them off to smooth it out... Anyone have any information on why these were added? Went to another store and broke another gun down and it had them as well..... Does not seem to be a defect.


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Old January 2nd, 2017, 08:16 PM   #2
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Just machining marks left over from the manufacturing process, they don't show and don't affect function, so nothing to worry about.
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Old January 2nd, 2017, 09:46 PM   #3
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My 9mm Shield does not show these ridges. Have to check my .40 full size and see but I do not remember seeing them before.
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Old January 3rd, 2017, 03:56 AM   #4
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Not sure if it is why they are there or not but since they are only on 45 shield it is my theory they provide additional drag to assist in slowing slide down a bit.

I feel no difference racking the 45 compared to my 40 and both are always loaded plus 1.






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Old January 3rd, 2017, 04:14 PM   #5
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Not sure if it is why they are there or not but since they are only on 45 shield it is my theory they provide additional drag to assist in slowing slide down a bit.






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You know, I had the same thought about this. My Shield 45 really throws the brass a long way.
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Old January 3rd, 2017, 05:02 PM   #6
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Not machining marks.... they are intentionally made that way, they are too pronounced and stepped to be poor machining.

I was assuming it was to help slow down the slide as it travels backwards as well. However, I thought this would be a really poor way to do that. You can see the brass that is scrapped off the case below the slide. seems like that would cause problems and possibly jams if uncrimped ammo was used.... I would still like to hear from S&W why they are there. My request to them has gone unanswered
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Old January 3rd, 2017, 07:57 PM   #7
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Quote:
Originally Posted by NathanRhoades View Post
Wondering why S&W put the machined ridges on the underside of the slide. Different from the 9mm and .40, and feels like crap when you pull back the slide if you have a full mag in. Attached a picture of the brass buildup on the ridges i'm talking about. This really seems like a poor addition and would like to machine them off to smooth it out... Anyone have any information on why these were added? Went to another store and broke another gun down and it had them as well..... Does not seem to be a defect.





Attachment 7818


I don't have the grooves which are depicted in your picture.
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Old January 3rd, 2017, 10:08 PM   #8
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The marks appear to have a slight curve, such as from a milling machine, this is just a part of fitting the parts on a mass produced pistol.
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Old January 4th, 2017, 06:52 AM   #9
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My Shield 45 has them, but none of my other four M&P's have them.

I also believe that it's to slow slide velocity.
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Old January 4th, 2017, 08:35 AM   #10
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My Shield 45 has them, but none of my other four M&P's have them.

I also believe that it's to slow slide velocity.
....and to grind up your ammo along the way...lol
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Old January 4th, 2017, 08:55 AM   #11
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....and to grind up your ammo along the way...lol
I may be wrong but I don't think so. This long lowered piece of metal is made to pick up a new cartridge and load it to be fired. And that is all. The only part of this piece seems to be used at the front of it. If I am correct then the "machined marked" surface wont make any difference and wont drag on the cartridges.
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Old January 4th, 2017, 10:47 AM   #12
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I may be wrong but I don't think so. This long lowered piece of metal is made to pick up a new cartridge and load it to be fired. And that is all. The only part of this piece seems to be used at the front of it. If I am correct then the "machined marked" surface wont make any difference and wont drag on the cartridges.


Well the loaded mag is DIRECTLY up against the ridges when inserted in magwell.
So when gun goes bang it DRAGS across the top cartridge on way back and strips new one on way back in to battery. So I still say its to reduce slide speed.



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Old January 5th, 2017, 06:16 PM   #13
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Well the loaded mag is DIRECTLY up against the ridges when inserted in magwell.
So when gun goes bang it DRAGS across the top cartridge on way back and strips new one on way back in to battery. So I still say its to reduce slide speed.



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Agreed.

That ridge that runs down the middle of the underside of every auto-pistol that I've ever owned usually has a brass colored residue whenever they're broken down for cleaning.

I believe that the ridge is rubbing on a brass case both when retracting after a round is fired, and against the next round in the mag while the top round is being fed/moved forward as the slide returns to battery.
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Old January 5th, 2017, 10:59 PM   #14
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Agreed.

That ridge that runs down the middle of the underside of every auto-pistol that I've ever owned usually has a brass colored residue whenever they're broken down for cleaning.

I believe that the ridge is rubbing on a brass case both when retracting after a round is fired, and against the next round in the mag while the top round is being fed/moved forward as the slide returns to battery.
Kinda like a hacksaw inside your gun....lol grind gring grind naw naw naw
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Old January 7th, 2017, 06:04 AM   #15
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Anybody know who/how to contact at S&W to find out the deal here? So far I really like the gun, it shoots well for a BUG, I've had no issues with function, but I like to know how my guns work and why they operate the way they do. I want to know why these ridges are here and what they are for.....
Thanks,
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