It's actually interesting how .45ACP, even in its cardboard boxes (the kind with a plastic tray...I think there's about 500 rounds in there) is HEAVY, but 1000 rds of .223 isn't bad at all. I have another box with about 250 rounds of 12 ga. 10 pellet 00 buck, which isn't nearly as heavy as you'd expect-there's a lot of empty space, plastic, and powder taking up all the room. I suppose the same goes for the rifle ammo.....more powder pushing less lead=lighter tactical wheelbarrow of ammo.
Kinda adds to the old .45 ACP "slow & heavy" thing