I keep everything in this minus my ammo can of range ammo.. Rifle, 10 extra loaded mags, bottle of oil, boresnake, chamber flag, some coyote calls, sharpie, CAT tourniquet, and some rolled gauze.
Then I keep my other guns in their respected cases with ammo in their respected cans. Remington 700 has a notebook and pen and a boresnake in it's case, shotguns just have the shotgun in the case, handgun case just has the gun, spare mags, and boresnake in it. So yeah, my AR case carries the necessities as it is my "go to" gun. The Glock never is in a case unless it has to be, if not, it's on my body and it's to get me to a bigger gun.