M&P 357 Sig Recoil Spring?

[kcofohio]

I have recently bought a 357 Sig factory barrel for my M&P 40. I'm wanting to get a bit stiffer spring for shooting 357 Sigs. In searching the internet about spring poundage, there seems to be much information at odds with each other. Some say M&Ps in 9 & 40 are at 15 lb., and the 357 is 16 or 17 lb. Galloway says they're all at 17 lb. And Galloway's next step up is 20 lb. Brownells stated that S&W doesn't list a poundage for a replacement factory recoil spring.
I'd like to know what other members here may have done or not done.

 

[fxvr5]

Galloway appears to offer 18 lb springs, too.

https://gallowayprecision.com/smith...bled-guide-rod-for-m-and-p-full-size-pistols/

We offer fully assembled units captured like factory in 15lb, 18lb, 20lb, and 22lb.

The full size pistols both now ship with 18lb, we recommend the 20lb for the 9mm and 22lb for the 40 models, the 15lb spring is for light hand loads only.

 

[kcofohio]

Galloway appears to offer 18 lb springs, too.

https://gallowayprecision.com/smith...bled-guide-rod-for-m-and-p-full-size-pistols/

We offer fully assembled units captured like factory in 15lb, 18lb, 20lb, and 22lb.

The full size pistols both now ship with 18lb, we recommend the 20lb for the 9mm and 22lb for the 40 models, the 15lb spring is for light hand loads only.

I guess that is where my confusion is. Wolff spring says factory is 16 lb.
For $23 apiece and free shipping, I think I will order both the 20 & 22 lb. from Galloway.