Hello, this is my first post

I have a 9mm sigma that I really like and am working to optimize the bad girl to possibly use in stock class idpa matches. I am new to shooting match and want to set the pistol up as well as I can.

For the trigger I have replaced the striker spring with a 3.5 lb wolff, polished all interacting surfaces, gotten rid of the useless pigtail and replaced the over spring in the sear block with a much lighter spring I pulled out of a bin at my local hardware store. The trigger is downright sexy and 400+ rounds later the gun runs flawlessly.

Here is my question:

How would changing the stock 18 lb recoil spring to a lower power (15 lb) affect performance?

Would it be better to increase the recoil spring weight for a comp type setup? Springs are available in 19 20 22 and 24 lb.

I don't have any experience with this type of modification and appreciate your collective experience and advice!

Welcome to the sigma club ZenDaddy!

I don't know how to hot rod the sigma; I've chosen to keep mine stock.

Hopefully, others will chime in.

Post often,

Lee

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SD9VE, American perfection!

I can't help much with hot rodin the Sigma but I have shot 2 IDPA ''type'' matches with mine (stock) and did pretty well. I have another match in 2 weeks and I'll give her all she has.

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The kool-aid Sigma drinker

357, try not to embarrass the snobs too much! LOL!!!!!!

Can't wait to hear about it! Good luck my friend!

Sigma Rox!

Lee

__________________
SD9VE, American perfection!

What ammunition do you shoot or intend to shoot? The goal is usually to keep muzzle flip to a minimum and a lighter recoil spring may help you there providing you have enough energy for reliable cycling.

The lighter the recoil spring, the more you batter the frame as the slide goes back and slams against the frame stops. The heavier the spring, the less likely it is to get reliable extraction, ejection and the more you batter the frame as the slide goes forward. Recoil spring weight needs to be optimized for the load you are using. Were I you, I would stay with the factory recoil spring weight and use loads that operate within the same pressure, velocity and energy standards as factory loads. Of course, were I you, I would have not changed out any of the springs, and I especially would not have replaced a gun spring with something out of a bin at the local hardware store. But, that is just me.

Shawn, Thank you for your response. I agree that it is generally unwise to fool with a carefully engineered design that involves the potential of lethal force. If I were going to use this pistol as a carry or even home defense weapon I would not even consider "hot rodding" the gun. However, I want to maximize its potential as a match shooter only.
Since I am new to the sport I have to expose the back of my wet ears to you and ask for help. Sooo correct me if I am wrong: The only negative risk in changing the striker spring for 3.5lb is the potential for a light strike misfire. The only negative risk in changing the sear block overspring for a carefully selected lighter replacement is a loss of trigger action resulting in no strike at all. So, the only risk I have incurred so far is the risk of the gun not going off when I need it to.
Changing the weight of the recoil spring carries a different set of risks entirely. Overloading the frame could be dangerous and having a ftf or fte could potentially result in an open breach discharge (unlikely but certainly possible).
This risk is why I am hoping to hear from folks who have more experience than me.
I am not a reloader yet and will be firing standard 115g factory fmj. My inclination at this point is to experiment with a 15lb recoil spring. There is no safety disclaimer on any website I've seen selling the reduced power spring and guide rod, I take this to mean that the frame will handle it just fine.

I have played with replacing recoil springs on pistols and have a feel for what the results will be. Although I haven't messed with my Sigma I don't see how they would react to a change in spring weight any different than a mil-surp pistol.
My experience has been when the recoil spring is replaced with a heavier spring the felt recoil goes down, the reliably of the action MAY be less due to the extra force required to open the slide (although I have never had this problem with standard factory ammo) and it will be harder to rack the slide to chamber the first round.
Using a lighter recoil spring MAY give more reliability with lighter reloads, makes the slide easier to rack back. With factory loads the recoil will be harder, throw the brass farther, and batter the frame more during recoil.
For me, when using factory loads I might consider using a heavier recoil spring to lessen felt recoil but I would never go lighter. However with a 9mm in a Sigma, for me, the recoil isn't much and I wouldn't mess with it.
Seems pretty easy to shoot as is. However YMMV
-greg

And the answer is.............
The Sigma recoil spring is already optimized for the 9mm ammunition you have to use to make (minor) power in IDPA and USPSA/Production.
Buy a spare stock spring/rod assembly to put in your range bag, and go shoot!
Good luck, and have fun.

IDPA Match Director

Thank you for the responses all.

My experimental tinkering nature combined with a complete lack of common sense on my part (yeah I was the kid that had to touch the stove to see if it was really hot!) will probably lead to at least an experiment with both a heavier and lighter setup. I would lay odds however that I will end up doing exactly what OKC05 has recommended. It is very nice to have a quality firearm at such a price that I can afford to indulge my meddling ways.
Thanks again and it is good to be here.

The OEM spring is perfect for all most all loads except max and major reloads.