I only have one and it came with 1k 9mm from Brownells a couple years ago. I have only ever used it taking to the range and putting my spent brass in it. I'm just personally more comfortable with GI metal ammo cans for ammo or component long term storage.
Same here, I'm just dismayed at what they are charging for USGI ammo cans these days... but you get what you pay for.
I've got one of those MTM AR mag cans, same thing as their ammo cans just fitted with slots for AR mags. It's OK, but when I've got it stuffed with loaded 30rd AR mags (about 20 of them) it's pretty heavy and it makes me nervous. I just don't trust the plastic handle or, more so, the plastic latches. I really wish the latches locked down.
The one I own is labeled as holding a flat of shotgun ammo. With 1-1/8oz loads, that's about 35#; I have carried by an end grip, holds up fine.