I think that when the BATF agents did their incompetent and heavy handed raid on the poor guy with the dummy grenades that it caused a fallout with the NRA at the time. Before then the NRA and BATF were pretty much together on everything. The fellow had converted some dummy grenades to fire caps off when thrown, etc. He was thrilling kids on the 4th of July with it when someone complained. That caused the raid to happen later. They convicted the guy of having illegal explosive devices. The Federal judge said that he had made the devices where they "could" be loaded with explosives an used then. Thus that was when the NRA and the government parted ways.

I got this one example many years ago. Someone made a mold and was casting new iron bodies for the practice grenades. They would drill and tap it for the surplus grenade fuse ends and handles. I was going to make one of those joke "Please take a number"displays. But I took too long and now it would freak people out if they saw it.