Why doesn't S&W use the same slide for 9mm and .40

[Mark]

A co-worker has been running an M&P .40 with a conversion Storm Lake 9mm Barrel for over a year now and has not had any reliability problems and the gun shoots very accurately. I played around with the 9mm in the .40 slide and found that the extractor fully engages the case and ejection is positive. Given that .40's don't have accuracy issues and from what I've experienced guns using the Storm Lake barrel are both accurate (I'm talking accurate) and reliable and some knowledgeable people believe the 9mm slide itself is a big part of the problem.....why not just use the same slide with some breach face changes?

[23JAZ]

Big surprise but it boils down to money. The company I use to work for supplied the pins for all S&W guns and I can say for a fact S&W is no different then any other company, they're cheap! They want to save money wherever they can, so if you can make a slide using less steel because its firing a less powerful round, they will. I believe they use a lesser grade steel and that contributes to the accuracy issues everyone is seeing e.g. more flex, and wider tolerances.


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[Luke]

So this whole time all I had to do it buy a 40 and put a conversion barrel in it?

[ranger]

I have a S&W M&P PRO 40 (the long slide version) and it shoots great with the Storm Lake 9mm conversion barrel. So good that I sold my M&P PRO 9mm.

[orionz06]

I believe they use a lesser grade steel and that contributes to the accuracy issues everyone is seeing e.g. more flex, and wider tolerances.


I had not heard this before. Any more to it? I also can't see a different grade of steel showing the variances we are/were seeing with the 9's either.

[23JAZ]

Lesser grade steel is inherently more malleable. I've got no scientific proof to back it up. This is just my opinion as a QA Engineer / gun nut. What I can say for sure is I owned an M&P 9FS and got rid of it for a Gen 4 G19 that runs a slide with thicker walls then an M&P-OS


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[orionz06]

What I was getting at is with all of the issues identified with that gun the material has never been a concern, that I was aware of. There are lots of other things beyond the grade of steel at play to begin with, especially considering the coatings and treatments used on the gun now and in the past. I think we're pretty far from S&W saving money on the slides by way of a different grade of steel.

[htomeheb]

What I was getting at is with all of the issues identified with that gun the material has never been a concern, that I was aware of. There are lots of other things beyond the grade of steel at play to begin with, especially considering the coatings and treatments used on the gun now and in the past. I think we're pretty far from S&W saving money on the slides by way of a different grade of steel.

I dont recall all the details, but I've heard it argued that they were worried about it saying "STAINLESS" down the slide, which would be a fairly major influence on material choice. The argument also went into coatings making it a moot point anyhow, etc.

[rsa-otc]

This is what I did when I went front a M&P 45 to 9mm. My only issues at this point have been extraction shooting left hand only, which don't occur when I use the 40 barrel (I'm right handed). Since I only shoot my own reloads and the cost difference between reloading 40 vs 9 is minimal, I have been debating whether to get an apex extractor or stick to 40. If I was shooting factory ammo the extractor would be installed already.

I want to get a few more rounds through the gun and then I am going to do a write up of my journey.

BTW what recoil spring are you running with the conversation barrel?

[ranger]

This is what I did when I went front a M&P 45 to 9mm. My only issues at this point have been extraction shooting left hand only, which don't occur when I use the 40 barrel (I'm right handed). Since I only shoot my own reloads and the cost difference between reloading 40 vs 9 is minimal, I have been debating whether to get an apex extractor or stick to 40. If I was shooting factory ammo the extractor would be installed already.

I want to get a few more rounds through the gun and then I am going to do a write up of my journey.

BTW what recoil spring are you running with the conversation barrel?

I am running the S&W M&P PRO 40 (5 inch) with an APEX trigger, APEX competition kit, stock PRO fiber optic sights, and STOCK 40 recoil spring with the Storm Lake 40 to 9 barrel and M&P 9mm magazines. Normal practice load is 135 Bayou bullet and 3.8 grains of Bullseye and Tula primers when I run out of the 135s I will switch to 124 Bayous and WSF (finally found some WSF). No issues running the 9mm conversion with the 40 recoil spring so far.

[john c]

My understanding is that the recoil springs are the same in 9mm and .40 M&Ps.

[rsa-otc]

Yes they are both the same, the catch comes that the M&P 40 slide is heavier, so you "MAY" need to lighten the RSA spring to run the less powerful 9mm.

[rsa-otc]

I'm running the M&P40FS model with the Storm Lake convertion barrel with the Apex DCAEK installed. Warren rear sight with an aftermarket front sight.

I was loading 147 SNS casting FN bullets over 3.3 grains of Buyseye using Winchester Primers. When I started having extraction issues WHO I moved up to book max load of 3.5 grains of Bullseye figuring it was too weak a recoil impulse but still excountered issues in testing even with a 15lb recoil spring. I have no issues WHO running 180 grain 40S&W at 125 PF with the stock RSA.

It is less than a dollar per box to reload 147 grain 9mm vs 180 grain 40's, although it is easier to find empty 9mm brass to reload.

[Mjolnir]

Why carry the extra mass if it's not needed?

Also slide velocity window must be considered as well.


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"One cannot awaken a man who pretends to be asleep."

[NuJudge]

I've run a lot of 9mm rounds through Beretta 96 pistols, just changing the barrel. I did not even have to change the magazine. Beretta runs the same recoil spring weight in both 9mm and .40 caliber 90-series pistols. Some of the vendors say the extractors are the same, 9mm and .40, but I broke a .40 extractor and put in one of the new one-size-fits-all extractors, and suddenly I had failures of the extractor to snap over the rim, causing a jam. I tried another one-size-fits-all, with the same result. I found a new, old stock .40 extractor, and everything is good again.

[rsa-otc]

Quick update:

After another range session with several FTE with the 9mm barrel I decided to pull the trigger and get the Apex extractor. When I went to replace the old extractor I found that the top of the hook was chipped. It almost looks as if there was a void in the MIM casting leading to a premature failure. I'll give an update once I put a few 100 rounds down range.

[rsa-otc]

Finally photbucket allowed me to do something. Here's a picture of the chipped extractor.

http://i1188.photobucket.com/albums/z417/rsa-otc/20151210_113853%20%20a.jpg