Okay. I see the problem here. Shell doesn’t mean shotgun round. Bullet and shell are technical terms for the bit of a round that comes out of the business end of a weapon at high velocity. A bullet is a single, simple solid mass that follows a ballistic trajectory and just imparts kinetic force into whatever it hits. A shell is anything more complicated than that. Shotguns are just the small arms weapons that are most likely to use shells, but anything can, and it doesn’t have to be buckshot to be a shell. Even something as simple as a tracer round is technically a shell.