Ammo.

[Frankie]

a better idea would to have it so your ammo is counted based on how many boxes you have in your inventory instead of having to load it all into your gun by pressing D 100 times. a separate inventory type thing just for ammo could always be made to avoid any issues with weight and inventory space. it would make a lot more sense that way since each time you reload your gun, you would be getting the ammo from your inventory and not some magical compartment in your gun that stores 10k ammo :P