If it dose not have a firing pin, it is not a firearm, but ammo.
I made a lot and tested them back in the bad old days.
We used throw aways and not fancy ones with firing machanisms, because if you do not have the firing pin in the powerhead, you theoretically cannot get a AD.
Nine times out of ten, the shark approaches you when you have speared a fish and then all you have in your hand is a piece of aluminium tube, so your powerhead is useless, unless you have a fancy one with a firing pin, which is highly illegal.
If they catch you withit, you will be arrested, for having an unlicenced firearm ( PAPPA WAG VIR JOU )