I believe there are other factors involved as well. I own a Kahr PM9 autoloader, which I believe weighs about 14oz, and has a polymer frame. I also have a Taurus 905 9mm all-steel revolver that weighs about 24oz. Even though the revolver weighs much more, it has a heftier recoil than the Kahr, with the same loads. I believe the Kahr, having a polymer frame and locked breech design, soaks up alot of the recoil. I've shot +P+ loads in it with no pain and very good accuracy. I can't stand to shoot more than a cylinder or so in the Taurus as it really makes the palm of my hand sting.
Lou