That would make it like the old firing system we had for one of our smoke grenades, the HC-C1A1... It had a .45 Colt cartridge to fire it. The cartridge was filled with lead and only had a small channel through the center containing FFFG black. It used a large pistol primer and would back out upon firing so you could hand remove it once cold. The originals were marked .45 GRENADE...no living example in my collection. These were a full size pistol cartridge though, that's why I wondered... Neat example.
I've heard the Adrian was a VERY comfortable helmet.