Unless the plan is to specifically plink or target shoot while out on the trail, I leave the .22 and take a full sized defensive caliber. Anything that needs to be shot will respond to the 10mm more favorably than the .22.
I could be convinced to bring a full sized gun and a light (317) .22 and a couple boxes of ammo if plinking is on the agenda. Heck, a 317 and 100 rounds weighs less than a spare box of 10mm ammo anyway.
100 rounds .... dude thats almost the same as being out of ammo