When I first looked into the hollow point of these bullets they reminded me of Gold-Dots. Not that they actually look alike, but you can tell there's more to it than just a cone shape punched into the nose. The first thing I noticed is a tiny hole at the center shaped like a six-pointed star. It looks just like a Torx screwdriver socket but smaller than any I've ever seen. I grabbed a sewing needle and tried to stick the eye of the needle in the hole but it wouldn't fit. The point of the needle went down just about even with the case mouth. SIG calls it a "Stacked hollow point bullet design with additional hollow point cavity." The secondary cavity may be deeper than the primary is. My guess is the bullet is made in a way similar to the Gold-Dot, where a bigger, more complicated shape is formed in the cavity, then another die squeezes it shut (mostly), leaving it pre-stressed where it will split when it expands.
I haven't shot any of this ammo and likely won't until summer. I'm going to take the pistol frame off my Mech-Tech CCU and put the 5" pistol back together. My old recoil spring is under 6" long, which I think means it needs to be replaced. It's an 18.5 pound variable rate which would ~= the 18 pound spring it originally had. I'll talk to someone at Wolff and see what they recommend for +P ammo only. 20 pounds may do the trick. Then I'll see how the Sig and Cor-Bon +P ammo I still haven't shot work in it. I have 3 15-round mags and might load one of the spares with the 230 grain SIGs and the other with the 165 grain Cor-Bons if everything works well. I'd like to stick with the Cor-Bons for the 15+1 in the pistol if possible because 573 ft-lbs ME should deliver more energy in-target. My guess is that the recoil wouldn't be much worse with the bullet being so light. The 471 ft-lbs ME of the SIG ammo is nothing to sneeze at but if the gun functions well, and I do, why not have the extra 102 ft-lbs? That's getting up around 10mm territory, which in the SIG V-Crown is 624 ft-lbs ME.