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Johnson Submarine Gun (SMG) cartridge powered

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popgun pete

Well-Known Member
Jul 30, 2008
These SMG spearguns first came out in the late sixties and I remember checking out the single barrel version at Alcock & Pierce which is/was a sports store in Melbourne. The ammo that they used was a limitation as although based on the range of Ramset .22 cartridges for power tools like nail guns, you needed the "Sub Ammo" plastic sleeves that waterproofed the rimfire cartridge and which the tail of the spear stuck into at the front end in order to stop the spear falling out of the speargun's barrel. They were non-floating after the shot weapons and more suited to scuba divers conducting spearfishing at depth. Tapmatic Corporation in the USA manufactured them for about ten years, then at some time Crocket and Co(?) in New Zealand bought the rights and the remaining stock of speargun components and subsequently produced the SMG in New Zealand. Being banned nearly everywhere but the USA destroyed the market for such guns. Tapmatic told me that they produced about 2500 guns, but how many more were made or assembled in New Zealand is unknown. I have seen a couple of the New Zealand guns and they are identical to the US guns being the twin barrel versions. These guns turn up every now and then on auction sites and are generally in good condition as they could rarely be used if you did not have the plastic ammo sleeves.
SMG brochure.jpg


SMG Reel.jpg

Johnson SMG patent.jpg

popgun pete

Well-Known Member
Jul 30, 2008
If you look carefully at the patent drawings then you will see that the SMG trigger mechanism is just a pull down sear lever mechanism, as was used in the first French Arbalete, which fires a long captive bolt that acts as a firing pin. Until I found the patent the innards were a mystery to me, but coincidentally in my own cartridge gun I used a similar mechanism based on a spring gun trigger mechanism which operates the same way. Unfortunately when the rules changed I had to destroy it, however it was not a very practical weapon, but seemed a good idea at the time.
SMG handle and trigger mechanism.jpg

Ramset .22 spear pistol 2.jpg

My ramset pistol for underwater hunting, built in the early seventies. The bolt is cocked by drawing the top lever back and then moving it sideways in a dogleg gate which acts as a safety. You inserted the shaft, which was retained by an internal collet at the rear of the stainless steel tube barrel, and then put a ramset cartridge into the breech. The breech was then screwed shut with about 3 turns of the barrel, the line was rigged and once you were ready you flipped the lever upright and you were then ready to shoot.
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