The Americans experimented with a 16mm aircraft cartridge called the Vega, the bullet looks old enough to qualify for WW2 vintage.
I'd be very careful / cautious with that round. It looks to me that it might be an Oerlikon 20mm armour piercing, and possibly incendiary, round. Leave the nose cone alone because you don't have any idea what is under it.
You should never pick up any type of round, casing or anything anywhere near a military training area.



























