[WeeWilly]

You don't have to be Issac Newton to understand that if you are shooting a wide range of power factors, with some of those loads a single spring weight will be suboptimal. There are two places to watch as it pertains to what recoil spring setup will be optimal for a given load.

The first area that seems to crop up is feed reliability. Some people report feed issues when shooting some of the hotter commercial offerings like Underwood, Buffalo Bore, etc. There is a thread in GT right now regarding a G20 owner that found a heavier AM spring cured a failure to extract issue he was having. Others report double feeds, etc. (Sometimes these are addressed with heavier magazine springs). I have a lot of 10mm down range from my Glocks and never really experienced any feed issues regardless of the RSA weight I was running, so YMMV.

The second area to watch is slide to frame battering. With very hot loads, the slide velocities can be quite high. Things like grip, stance, arm strength all will change this dynamic, much like it does for feed reliability with other calibers and lighter loadings. The way you can determine if your recoil spring weight is keeping the slide from battering the frame when shooting a given hot load is after a few boxes of the stuff, field strip the gun and look at the plastic right in front of the front slide lugs. This is the area the spring perch part of the slide will impact the frame if it is going to under a heavy loading. You will start to see the imprint of the slide there. In extreme cases that area will start to peen over and can cause function problems, but that usually takes quite a bit of rounds.

I use a 22lb flat wire ISMI spring on a stainless guide rod for my G20's. It keeps the slide off the frame under my heaviest loadings and will cycle even lighter 40S&W loads, although I do install the stock guide rod if I am running a lot of 40 target loads through the gun.

The G20 is a marvelous gun, enjoy it.

 

[WeeWilly]

So far the ammunition I have is Sig V crown which by the reviews achieves advertised velocity of 1250 I believe. Then I have the double tap that I mentioned above 165 and 180 grain. But if I am going to order ammunition it would be 175 grain Winchester silver tips if I ever see any appear on GunBroker;

I am tempted to order some Underwood maybe 165 or 180 grain jacketed hollow point.

The Xtreme penetrator is very interesting but I imagine that is considered a Hot Load.

If a load actually achieves the velocity of 1250 to 1300 from a G20 at 180 grains, from my reading I'm led to believe that is considered a full power factory load, probably a little under the max load guidelines for companies to meet their liability standards.

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1250 to 1300fps for a 180gr jacketed is a "full 10mm load" and some.

Using my OEM barrel, I start getting case smiles (shearing of the case down by the head by the feed ramp) if I load much above about 1325fps for a 180gr jacketed.

Like Danny, I found Underwood and BB both pretty much reach "advertised velocity", Double Tap, not quite as much (but plenty for any practical application). I have read great reports of the newer SIG V Crown offerings, but have not shot any myself. Again, 1250fps is a lot of handgun in a 180gr bullet.

I have found the optimal "SD" style loading is a Gold Dot at 1150fps. It gives me a ton of terminal performance and is very manageable for quick follow-up shots. For trail work, I load a 200gr WFNGC bullet to 1200fps. That is very achievable for less than max loadings in a G20 and a little bit hot for my G29, but still not risking breaking anything. That bullet is an express freight train.

Good luck, have fun.