I get 540 rounds on stripper clips into a .30 cal can.
I put my ammo on clips then print out a sheet of paper with a description of the ammo. I cut the 8 1/2 x 11 sheet of paper in half so that I have two 8 1/2 x 5 1/2 sheets, each with the description printed on them.
I take three clips, stack them, and wrap them in one of the sheets and tape it. (Make sure no tape gets on the ammo.) That holds the ammo together, helps protect it, and labels it so you know what you got.
You can stack 12 of these packs edge down in the bottom of the can. That leaves room for 6 more packs along the top. It fits perfectly with a little bit of room for cardboard spacers for padding, and a bit of room on top for clip guides. You can use a couple bandoleers as padding on one side and pack their straps in the spare space too.
I’ve had ammo stored like this for 12 years and it seems to work well.
Anyway, if I can get 540 rounds on clips in a can then you should be able to get a whole lot more packed loose.