You are a facepalm, OP.

you should not know what a grenade casingg looks like. in a ideal society, average people shoukd not know anything about any of the weapons. if they do, they either were using them (which is bad), or they were being used against them (which is worse).

I don’t know what they look like either - what is your point?

Sniping is a practice not a caliber size. You can snipe with 40mm grenades if you are using the right hardware.