When looking for places to reduce weight for backpacking, the last place I will look is my firearm.
That about says it. It's true that if a backpacker doesn't pay attention to the weight of his load, he greatly reduces his enjoyment of his hike.
But you can get carried away. Cutting of the handle of your toothbrush is not going to make any difference to your hike, except to make brushing your teeth a bit less convenient. You'll save, what, maybe half an ounce? An ounce? Will that REALLY make a difference? No.
Same with the firearm. You need to balance the priorities. What kind of critters are you concerned about? Outlaw bikers or grizzly bears? Coyotes? Wolves? Mountain cats? Or two legged varmints only?
Carrying a .50 BMG with 2000 rounds of ammo will take care of most problems you might encounter, but it's probably not very practical. But once you've dropped down into the handgun class, is there really that much difference in weight between a .357 and a .22? No, not really.