I don't have as many guns as a lot of you guys, but when my collection was at it's largest, I rarely brought EVERYTHING.
Back in the day, we'd grab the guns, the ammo, and pop bottles and milk jugs to shoot at and head to the quarry.
Now, I have a backpack that I stuff with all of the magazines and ammo I'll use. I generally don't spend all day at the range, so about 100 rounds for the FAL, and maybe 100 for the handgun will usually get me by. (But then, my range is only a few minutes away, so I can go every day should I want to.)
*shrug* Don't have a spotting scope, and I use Army rubber earplugs instead of bulky muffs. I carry a roll of duct tape in the car, so that solves my target mounting troubles.
If I wanted to carry more ammo, I guess I'd get a larger bag. But you can stuff a lot of boxes of ammo and FAL mags into that one little backpack.