According to everything I have read the 9mm and 40 M&P Recoil Rod/Spring Assembly are supposed to be the same.

I have a 9mm and a 40 M&P both bough in the last 3 months, both are 4.25" Pro models. The 40 has a spring assembly with green paint on the spring and the 9 mm has blue. I recently bought spare spring assemblies from Speed Shooter and they are listed as M&P 9/40 Recoil Rod/Spring Assembly. They have blue paint on the spring.

Is S&W now using different spring assemblies on the 9mm and 40?

If not why would the 2 assemblies have different color markings?

They used to be the same, but newer production uses different springs - one blue and one green.

That is What I thought. Glocks use different springs for the 2 calibers was suprised that S&W did not. Now to find some that has the 40 in stock. Speed Shooter just recently got the ones I bought back in stock. Have owned Glocks for years, just recently became a S&W owner. Parts availability is one of the biggest differences I have found so far.

Maybe I'm wrong but I believe gen 1, 2, and 3 Glock's used the same recoil springs for at least the 19/23 and 17/22's and 26/27's.

Like you, my Pro's have difference colored springs. Sure does make sense to me considering the big difference in pressure between 9 and 40.

I know my Gen 4's are different, I will have to check on my Gen 3 G22. OK, I checked Gen 2 and Gen 3 do use the same on the 9 and 40. I am surprised with the different in recoil between the 9mm and the 40.

The M&P 40s' use a heavier slide than a 9, the reason they can use the same spring. Just one other reason I don't care to use a conversion barrel in my guns.

All of the usual suspects (Midway, Brownells, Speed Shooters) show the same recoil assembly for the 9 and 40.

I've read that the green is for the .357 Sig, but will also work with the 9 and .40.
The blue is for 9 and .40 only.

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Randy

Ordered and received a S&W M&P Guide Rod Assembly for the FS .357SIG from G & R Tactical. It has the green on the end. Other the the color on the end I can not tell any difference between the two. Still don't understand why they are marked differently. I wish S&W would mark their guide rod assembly like Glock does.

BS, .40 & 9mm slides are virtually the same weight.

OP, as another already pointed out RSA used to be the same (blue spring) now they come with the green spring which used to be exclusive to the .357sig. However, blue spring should run .40 & 9mm just fine. .40 & 9mm also use the same extractor and ejector unlike with Glocks, which is why many find a 9mm conversion barrel with 9mm mags and .40 slide provide stock reliability.

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unrepentant M&P fanboy

Blue spring is approximately 15lbs., green spring is approximately 17lbs. I wouldn't advise using green with 9mm but blue should be GTG with .40 or 9mm.

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unrepentant M&P fanboy

Dear Doc, Weight them then look inside along the barrel, 9mm slides have less material in the side walls.

I no longer own a stock 9mm, however when I did I detected virtually no difference visually or comparing both side by side in hand. Per S&W Website .25oz weight difference between the models which is basically nothing. Myself and others have had very good luck with 9mm conversion barrels and OEM 9mm mags. I own a storm lakes for my full size, will likely be buying a compact version and the KKM for the Shield (when it comes out later this year).

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unrepentant M&P fanboy

Not Doc, but here are my results:

.40 slide 13.70 ounces, 389 grams

9 mm slide 12.95 ounces, 367 grams

barrel and spring assembly removed.

Thank you sir, 3/4 of ounce isn't going to make a difference. If you need evidence there is an abundance of members running cheap underpowered ammo flawlessly through their conversion barrels.

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unrepentant M&P fanboy

I can't speak for current production, but my M&P40 that is a year and a half old a my daughters one year old M&P9 have the same recoil spring.

I used to believe that too, then I did some research. Both the 9mm and .40S&W have the same pressure standard; 35K psi.

The .40S&W has more recoil because of a bigger bullet.

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Freedom isn't free.

Always fun debunked the "high pressure round" myth...

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unrepentant M&P fanboy

My .40c vintage 9/13 has a yellow-end recoil spring.
Is that the older one?

And thanks to Ras for saving us the .40 vs 9mm pressure angst once again.

I thought if you change the caliber you only needed to change the barrel and magazine. I haven't seen where there are springs to change with a barrel kit. Unless I am missing something...

StormLake S&W M&P .40 S&W to 9mm 4.25" Stainless Match Conversion Barrel SW-MP-9MMC-425-OP-00T

Sorry, I didn't mean to raise anyone's anxiety level. Just trying to spread the correct info.

This is true for just a simple caliber change. However, if you want to "tune" your gun for optimum performance, the recoil spring must be matched to the load.

Manufacturers try to make guns that will work reliably with a broad range of bullet weights. The reality of a recoil operated gun is that it can't be perfect with everything.

Initially, the .40 and 9mm both came with the same recoil spring; the blue one (I think it's 15 lbs). Then S&W must have realized that they were asking too much of one spring and they switched to the green spring for the .40 guns. It's a little heavier (I think 17 lbs).

I have a 9mm barrel and mags and I have fired about 200 9mm rounds through my gun while using the green spring. They worked fine, but the ejection was a little weak. If I were going to shoot 9mm regularly, I'd buy a blue recoil spring.

The result of this long winded reply is, the 9mm will work with the heavier spring, but it's not optimal.

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Freedom isn't free.

Blue spring is 15lbs, green spring is 17lbs. Initiallu green was just for .357sig, now green comes with .40 and probably a bit better match for .40 (never had a problem with blue spring & .40 though). For range use green spring and 9mm would probably work, but I wouldn't advise it for carry. If you want to carry 9mm with a .40 slide I recommend the 9mm CONVERSION barrel, 9mm magazines and blue spring.

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unrepentant M&P fanboy

Can anyone help me figure out how to order this part from S&W? Their site is not the easiest to navigate and I'm glad my life doesn't depend on being able to find the parts I want.
I've got a .40c with a yellow spring which I assume is 17lbs. From what I'm seeing here, optimal for 9mm conversion would be 15lbs.

Not 100% sure on the weight but yellow spring is used in 9mm, .40 and .357 compacts (probably 15lbs).

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unrepentant M&P fanboy

My FS 40 manufacture date of October 2013 came with the green spring.


I'd rather die on my feet than live on my knees

Then why does the difference exist? Why is the slide for the 40 slightly heavier? S&W would have a reason for this. Are you an engineer?

I'm actually a physician, according to S&W there is only .25oz of difference but even at .75oz it doesn't matter. 9mm/.40 in both 4.25" and 5" slides up until recently have all used the same blue recoil spring (and same extractor and ejector). Both 5" 9mm & .40 slides weigh more than their 4.25" model counterparts, yet the S&W engineers didn't see any need to change the recoil springs (we call that a clue), not to mention the CORE series and the added weight from RDS and suppressor sights which have also worked just fine.

You can also take the numerous accounts of guys who've used 40-9 conversion barrels with great results and surmise it works just fine (I do not recommend using a OEM 9mm barrel in the .40 slide). Of course I would never recommend carrying any pistol in a configuration with your carry ammo that you haven't thoroughly tested first.

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unrepentant M&P fanboy

There is a difference though it may not matter to most shooters.

There is what works and then there is what works best. So, the .40 is tuned to the best compromise for all the different common bullet weights for that caliber. However, a particular shooter might learn that for his custom 165gr bullet at 1,000 FPS a 16lb recoil spring is better than the 17lb factor spring. Another shooter might find that an 18lb spring works better for his 180gr loads.

So, yes, there is a difference. And, yes, that difference makes a difference. The thing is, most of us won't notice.


I have a 9mm barrel that I've used in my .40 with the stock recoil spring. Sure, the 9mm works, but it isn't the optimal set up. The ejection of the brass is weak. If I want the gun to be more reliable with the 9mm, I should change out the recoil spring.

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