At the range, the grenades would be issued one at a time to each soldier who would expend the grenade in training, typically under the direct supervision of an NCO. In the case of grenades, normally, the pin and spoon would have to be turned in for residue accountability, and woe be the soldier who pocketed one (pin or spoon) for a souvenir and got caught.
There is a little bit of flexibility for some residue. For example the brass from a rifle or pistol range is swept up and turned in by weight and there is a (small) window allowing for some lost or unrecovered, but in the case of explosives, mines, or larger munitions (i.e. mortars) there would normally always be a name, career and a court martial on the line for loss of accountability.
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