M&P9 Mag Differences w/Pics

[Tornado_Racing]

Just got a couple of new mags and thought I would post pics of the differences in tubes, followers, springs, and bases. All in all I have 2 different type of tubes, 2 different type of followers, 2 different type of base pads and 3 different type of springs. The Gen2 mag came with my M&P (purchased 8 months ago), the Gen3 mag was purchased shortly after, and the Gen4 just arrived.

As a side note only my HD mags stays loaded and all others I own are unloaded (including these). My M&P9 has roughly 500 rounds through it so these parts are far from being worn out. I do not have info on the Gen1 mag other than it had a black follower.

From Left to Right:
Gen4
Flat Color Tube
#9 Grey Follower
Square Hole Base Pad
Longer Black Spring

Gen3
Flat Color Tube
#9 Grey Follower
Round Hole Base Pad
Black Medium Spring

Gen2
Glossy Color Tube
Grey Follower
Round Hole Base Pad
Silver Short Spring

Same as above but all 3 mags stripped down

Mag springs with Arrendondo Extra Power Spring

One thing I did notice is the new S&W longer mag springs will lock the slide back while using the Arrendondo Base Pads. The other 2 stock springs will not. With the Arrendondo spring I only load 20 rounds as 21 is just too stiff. On top of that it puts alot of pressure on the slide as the rounds do not compress very much. With the new longer S&W spring I can load 22 rounds and the slide still locks, kinda best of both worlds.

 

[POTS]

Thanks for the info. Wonder why the spring got shorter? Did you have any issues with the 3rd style in stock form?

 

[Tornado_Racing]

Other than a tilted follower (Gen2 mag) I've had no issues with any mags. I have 6 mags total. 2 are Gen4's with the longer black spring, 1 is a Gen3 with the shorter black spring, and the other 3 are Gen2 with the short silver springs.

All springs have the same amount of coils & bends. Just seems the Gen4 springs are MUCH stiffer & longer than the others. I should retake the pics with a ruler and add wire O.D. but I need to find my calipers though.

 

[Tornado_Racing]

Here is a neat and easy mod to keep the base plates from sliding off during hard/slam reloads. This was the main reason S&W redesigned the base pads (to a weaker design IMHO)

I used an 8-32 buttonhead screw and Drilled/Tapped the spring plate where the catch notch is located. I had to cut down the 8-32 screw to 1/4" in length. The longer screw was hitting the follower on a loaded mag. I then drilled a blind hole in the 10-8 base plate so the screw would sit flush. I tried using a flathead screw but the threads were weak at the base of the countersink. After that I used a sharpee to color the aluminum, re-assembled the mag, and applied a tick of blue thread lock to the 8-32 screw.

This mod can be done using the stock plastic base plates but I would not recommend drilling the blind hole. There just is not enough material as the 10-8 plates are thicker.

Before Drilling, Tapping, and Cutting

After Drilling, Tapping, and Cutting

Assembled Mags

 

[GaryM&P]

Excellent informative post. Thanks.

 

[POTS]

Good idea. If I find that my 10-8 floorplates cause trouble I will follow your lead.

 

[SWMod10]

Great post..I wish they would go back and get rid of the square notch.

 

[Tornado_Racing]

Okay, I just measured the springs.

Gen2 .048" O.D. 5.5" Length
Gen3 .049" O.D. 5.75" Length
Gen4 .050" O.D. 6.25" Length
Arrendondo .049" O.D. 7.0" Length

From Left to right:
Gen4 Brand new
Gen4 22 round loaded for 24 hours (still locked the slide back)
Gen3 8-10 reloads or roughly 150 rounds
Gen2 8-10 reloads or roughly 150 rounds