Wear a shooting glove with a padded palm (golf gloves might work, too or bicyclists gloves). You will have extended endurance for practice without changing any dimensions of the gun.
The woven work gloves with the rubber friction mesh on the outside also work and are cheap, but last a long time while still allowing your hand to breath. You can cut the fingers off the glove very easily.
The rubber grip sleeve in addition to the glove might even be a better option.
Thanks for asking our advice. Good luck.
p.s. My shooting buddy has the same problem with his 500 Smith. So he loads practice rounds at half the energy level for practice, has a few full-power loads just to keep his hand in. With an automatic (if you want to keep the self-loading functional) you will want to install a lighter recoil spring for most of your range shooting, but that would solve your problem. But you will probably have to load your own light-recoiling ammunition.
Last edited by Lost Sheep; February 15, 2013 at 12:15 AM.
Reason: add post script