APHEATFSDSCBC

Armor Piercing High Explosive Anti Tank Fin-Stabilized Discarding Sabot Capped Ballistic Capped. A very huge and complicated round, which means its minimum gun caliber is 280mm.
(This type of shell is not real, obviously)

Commander: Load the APHEATFSDSCBC round!
Loader: Uhh, the fuck?
Commander: Damn it, just fire.