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I cannot tell you for certain but I dropped a 13# IMSI glock 17 spring in my M&P40 and it feels the same. Not scientific by any means but it is close enough for me.



Dan
 

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I'm about the same round count as you, and havn't had any problems. This weekend I put another 600 DR. I think I'm about to 13k. ah, I don't care, rounds don't count, targets do.
 

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I doubt you will ever break a recoil spring, it will just loose it's tension slowly. How often should you replace it. I don't think Smith has come out with an official answer I have a contact there I can ask and report back.



I will also give you my recommendation: I think every 5,000 is reasonable especially if using full power loads. Would definitely not go over 10k without a swap I think you'd be looking for trouble.



$15 for Speed shooter guide rod (one time purchase)

$8.95 IMSI spring (every 5k)

sounds like cheap insurance.



Dan
 

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Dan,



Did you see any difference in muzzle flip using the 13 lb. spring?



John
 

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John,

I didn't really. But honestly I am a poor judge and I didn't yet get to try it out with the timer to see if I am any faster with it. Like I said they seemed to be about the same. So I don't think it will be much different. Next time I will try out an 11# to use with my IDPA 40 Short &Weak load and a 15# for the 180gr Hornady TAP loads.



Dan
 

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Here is my questions and the responses(bold) I got from a S&W engineer:



1. People have asked what kind of interval you all suggest changing the recoil spring assembly. (our suggestion is 5000 rds. when we shot endurance guns we shot some springs over 10000 before replacing, as long as the gun reliably closes in full battery the spring is doing its job.)

2. What are the recoil spring rates you guys are using in the 9, 40, 357 (currently we use the same spring for all three 9/40 and 357, in the future we will be using a heavier spring in the 40 and 357 as far as spring rates they are something like this;



current 9/40 spring "marked blue"

10lb

k=3.7 lb/in



future spring for 40/357 and possibly 45 spring "marked green"

13lb

k=2.9 lb/in)
 

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I have some light loads in 9mm that i want to shoot in my m&p 9 when it gets here.

Where do I go to get a lighter spring?

thanks
 

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brownells has them. do a search under wolff, and look for reciol springs.
 

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Dan Burwell said:
Here is my questions and the responses(bold) I got from a S&W engineer:



2. What are the recoil spring rates you guys are using in the 9, 40, 357 (currently we use the same spring for all three 9/40 and 357, in the future we will be using a heavier spring in the 40 and 357 as far as spring rates they are something like this;



current 9/40 spring "marked blue"

10lb

k=3.7 lb/in



future spring for 40/357 and possibly 45 spring "marked green"

13lb

k=2.9 lb/in)


Thanks for the research, Dan. But what do they mean something like this, don't they know what the spring rate is? 10 lbs. seems awful low when the Glock spring rate is, I beleive 17 lbs. I am not a .40 fan myself but the fact that they are thinking of using a heavier spring but aren't yet would concern me a little.
 

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Dan and I talked about this last night, and came to the conclusion that the lockup mech night be different, camming over later in the cycle allowing a lighter spring, from the glock to the M&P, or even the XD where I used a 24lb spring.



I have a 15 lb on order to see how it shoots.



Glock stock is 17lb btw.
 

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Another thing that might come into play here is the barrel design. The coned muzzle barrel of the M&P has less friction during the cycling of the slide. I don't know for sure, but this is a possibility.



What is the cost of factory S&W recoil springs for the M&P?

Where can you buy factory S&W recoil springs?
 

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I bought a non captive rod from Speed Shooter Specialties and a glock 17 spring from brownells.
 

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don't know if the stocker will fit, the spring will with the SSS guide rod.
 

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They do know what the spring rate is. It is 10#. The fact that they are considering changing it, I don't think indicates that there is anything wrong with the 10#.



You need to understand that in the M&P design you do not need a heavy recoil spring to keep the barrel in battery during ignition. The only thing the heavier spring would is slow the slide's velocity down a bit. Do they need to slow its velocity more? NO, slowing the slide more would reduce the slides impact on the frame but the current combination has already demonstrated exceptional durability . So, I don't think changing the spring weight is really going increase it's durability much, maybe they think they can get take it just a bit farther.



This is just my guess: :roll:

I think the current spring set up was intended to run both 9 and 40 and would be easier to make just a single assembly. But now with the 45 coming out they are going to have a Blue (10#) and a Green(13#). So if it will run on the same spring as the 45 and you have to produce a new assembly anyway why not give it a try. I fit gets a little more durability, bonus.



I could be wrong all together and this is just evolution in action, they found it just works better with the 13# 8)



As far as factory replacements just give them a call ask for part #279740000 $6.36




As far as lighter springs IMSI makes an 11# spring which if the 13# IMSI feels like stock I may deduce that the 11# may feel lighter. But again I may be in left field (been there before and the grass was nice
)



Dan
 

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I just ordered the SSS guiderod and a 20# ISMI spring. I'm very curious to see what a difference it makes. Should arrive next week, so I should be able to post a range report the weekend after next. Given what I just read in this thread, I'm thinking, on returning to battery, the 20# spring is going to whip the gun out of my hands and sling it half-way down range (assuming I can even manage to rack the slide)
 
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