Well I fired my 20SF this past weekend with the new 24 pound captured RSA I ordered. The G20 shot beautifully. I fired some full power ammo, 155 grain JHP @1450 fps 730 fpe (PBRammo.com). I also fired 180 grain Remington UMC, which is a milder load.

The 24 pound RSA reduced battering to the frame. It doesn't necessarily reduce felt recoil, though the recoil seems to be more of a "push" backward rather than muzzle rise.

The RSA I got this time was from Glockmeister. Lenny Magills at Glockstore has the 22 pound RSA (Which I have already) but only Glockmeister seems to carry the 24 pound RSA.

Both springs are well worth the $$ if you like the extreme 10mm loads.

I was just looking at the very same recoil springs on Glockmeister; I noticed that they specifically mentioned using ISMI springs for their setups which reminded me of several posts on here about ISMI being awfully generous with their spring weight statements. Is your spring coming in at the advertised weight? I know you mentioned that your RSA worked well in your Glock so I suspect that they're definitely stronger but I just wanted to know how much stronger they are, in case I need to order a heavier weight in the off chance that the rating is off. Also: do you notice any difference in performance between the 22 and the 24 pounders that justifies getting one instead of the other??

I can feel the difference when I work the slide, but I can't say there has been a noticeable difference in performance between the 22 and 24 pound springs when I fire the gun. At least not yet.

I know that doesn't help you much.

Well it certainly gives me a place to start, at least for comparison purposes. I think I'll start with the lighter weight and see how that works; mostly I'd like to reduce battering to the frame when I occasionally cycle through some of my hotter loads to keep everything fresh. It's probably not a huge deal but I always feel like I'm being a little unnecessarily rough on my Glock when I run a hundred rounds of Underwood through it after going so easy on it with prior to that with two- or three-hundred Federal or Remington. It certainly couldn't hurt, I'm sure. Thanks for the reply.

Knowing the stock spring is 17lbs... and worked well for me with all,  I opted for a 20lb wolff spring just for the times I fire off the really warm loads but not effecting the normal target loads. 

Hmmmm good point! Maybe I'll just split the difference between the stock and the 22lb and get a 20lb.

I will say that if you are wanting to shoot the Underwood or Swampfox type performance, you will want to have the 22 lb spring.  Stock 10mm Glock 20 and SF springs were at 18lbs (measured).  Not sure about the G20 4th spring rates.

I do use the Wolff non captive steel recoil rod and 22 lb & even the 24 lb recoil springs that I use at times for testing the higher impulse ammo loaded to the UW,BB, SF and DT loads...

In my measurements of these springs they slightly more spring pressure at unlock and at full recoil before slide lock they show their rated weights. 

I guess I could measure my Gen 4 setup as it stands and see where that puts me... If it's a full 18lbs (or more?), I would think that I would definitely have to go with a 22lb+ to get the benefit I'm looking for. The more I think about it, the less necessary it seems to go with a 20lb over the stock 18 (I mean, what's two whole pounds, really?). Has anyone had a problem with the 22lb spring not functioning well with the (usually weaker) factory loads enough to warrant a lesser spring weight just to reduce issues at the range?

Just remember, not all springs are created equal ( so to speak )

Glock list the stock at 17 lbs , tho it has been known to measure different.... Some manf springs rated higher have been tested as less than rated so check into what you buy.

As mentioned I use the Wolff 20lb and the non-captive rod... they tend to be accurate in rating.   One thing is the non-captive allows a real fast change of spring if need be.

Btw, I put at least 1000 rounds of all diff loads thru my g20 before deciding to go up to 20lbs... Even with some of the atomic loads the stock spring worked fine tho the slide/frame was getting a bit of pounding.  Also, to heavy a spring can mess up the gun timing ( causing problems too ).