There's a G20 for sale here that would probably out penetrate the HK23 by a wide margin.
Actually we have done a bunch of testing, comparing apples to apples so to speak against standard steel penetration and then able to have delivered energy. Where you are taking the hottest loaded solid bullets in the 9mm +P+, .40 S&W, .45 ACP, 10mm, 45 super, .357 sig etc..
If you want to penetrate through something & then go on to actually have useable energy, you need lots of weight as well as speed.
In testing shooting through a 1/10th inch standard steel sheet and seeing damage to a second 1/10th inch sheet about 4 inches behind that, the 10mm is just slightly outclassed by the .45 Super because off the retained energy.
The best 10mm load from underwood was the 140gr at 1500fps (way better energy on second plate than the 100gr and 1825 fps)
The best .45 super load from underwood was the 200gr at 1100fps
The best .357 Sig load from underwood was the 115gr at 1450fps which was just behind the 10mm
Depending on exactly what you are shooting at, it may change, possibly in gel blocks the 10mm will do better, the problem is that usually you never hit a consistent mass all the way through, there will always be hide, bone, metal plates, wood, doors etc. that you will encounter, especially if you are shooting through some kind of light cover / concealment such as doors etc.
The 10mm outclasses all of them except the .45 super which has a slight edge, the .357 sig is just behind the 10mm and a great contender that you can shoot out of a lot of .40 S&W guns with a barrel change.
The 9mm was dead last despite everybody being in love with it these days.
However all of them are way behind when you pull out a 9" barreled Super Redhawk in .44 magnum, with the same maximum load ammo.
Also .50AE, .454, .460, .500 and the other magnum rounds way outclass everything else, but those are not rounds you carry in your average handgun.
If you want penetration through barriers & then useable energy after that in an average handgun without having to step up to the 10mm, the .357 Sig can be put onto a lot of .40 S&W guns and gives a pretty good account for itself.
