Personally, I would not consider the .30 cal cans because I always thought they were too small. When ever I buy ammo cans, I always try to get .50 cal or bigger. Also what I noticed is that I can never find in a good price or stock on 40mm cans. If you can sell a fat .50 cal can for $20, I think they can sell pretty good. As for princess auto, they sell their extremely rusty cans without markings for around $16 already. So, if you can sell a brand new ammo for $20 would be a pretty good deal to me.