Nemrod Filibustero

Thanks for your post Jeff, I really like old Nemrods, I have a few.
Cheers, Don Paul

The "Silver" series Nemrod spearguns, which are the guns that you are talking about, were all mid-handle, full length air tank spearguns with negative buoyancy. They came out around the same time (1966/67) that the Mares "Sten" first appeared, however the "Sten" proved to be a more versatile weapon for freedivers as it floated after the shot. Scuba divers like non-floating weapons for the fact that the gun stays down where they are after the shot. Once spearing on scuba began to attract criticism (sometimes unfounded) and was banned in certain countries then the heavy pneumatic spearguns became less popular. I bought the smallest "Silver" series gun, the "Comando", when they first went on sale here, but soon switched to the "Sten" as it floated after discharge.

The muzzle relief ports in the "Silver" series guns are in the wrong place as they are in the front sloped face of the muzzle, immediately behind the rubber nose pad, whereas they should be to the rear behind where the piston nose strikes the shock absorber anvil. This means that saltwater around the front of the piston is trapped in the muzzle behind the anvil. It can get out via a small leak path hole drilled through the side of the piston nose, but it tended to stay in there. That is why Nemrod supplied a short plastic plunger to stick in the piston and push it back a few inches to allow the insertion of a few drops of oil around that location. If it rusted then it tended to cause the piston to stick at the muzzle. Early piston noses were steel, later ones were changed to stainless steel.

If you look at a later gun like a Nemrod "Mariner" then you will see that the relief port ring has moved to the rear of the muzzle which allows water to rinse around the piston nose when washing the gun. The "Silver" series were some of Nemrod's most popular guns, but were probably more expensive to make than the "Clipper" style guns which gradually replaced them as the latter have fewer components and a moulded plastic grip which is also a pressure bulkhead.

It sounds like you had your Nemrod "Filibustero" (the longest "Silver" series model) pumped to well over the recommended pressure limit, those guns had a 35 mm diameter outer tank, so they had a higher compression ratio than the "Sten" which has a 40 mm diameter outer tank. Both guns have full length air tanks, unlike the classic rear tank models. Usually you put less air pressure in higher compression ratio guns as when cocked and ready to shoot the pressure in the gun climbs to much higher levels. I once made the mistake of pumping a 30 mm diameter outer tank gun, which I had just purchased, up to the pressure that I would normally use in a "Sten", it too had a full length air reservoir and I was judging the pressure by the effort to push the pump handle down. When I came to load the gun I could only get the shaft slightly over half way into the inner barrel, any more effort and I was going to bend the spear. Then I realised that the gun had a much higher compression ratio, it could not use that pressure level, so I removed the tail cap, put it into my diving glove and used the detached spear tip to bleed some of the air out so that I could continue diving with the gun. Fortunately it had a stem type valve rather than the ball type so I did not have to worry about damaging the valve.

Just so other people understand what we are talking about here what you call a plunger is the piston that pushes the shaft from the gun. The plastic rod or plunger that I was referring to enabled you to push the piston back without it jamming in the nose of the piston. It had a rounded tip and was about 9 cm long with a larger head at the pushing end. If you used the spear tail to do the same job then conic friction would jam the shaft in the piston, which is what it is designed to do, so it may be difficult to free the shaft again. I found that plastic plunger very handy for use on other guns as well. The sticking that I am referring to is when the guns were stored and the pistons rusted onto the shock absorber anvil, not sticking after the shot. This was with the ordinary steel nosed piston, my gun only received a stainless steel nosed version when I replaced the piston years later.

Your experience with the "Sten" shows what happens when the inner barrel muzzle threads strip, the muzzle flies off taking the nose cone with it and the outer tank as well. Those test fire shots out of the water may have done the initial damage before the muzzle threads gave up when you actually fired the gun underwater. I have had my old "Sten" up to 40 Bar (600 psi) and never blew the muzzle off the gun, however it was a two handed loading job with a custom made loading bar and was nearly impossible to load in the water. These guns rely on water in the inner barrel to keep the muzzle impacts down if you use high pressure air in the gun.

The SMG production was sold to a New Zealand company, they made some guns (probably from stock parts which they received as part of the deal) and soon disappeared. Technically not a firearm in the USA, the SMG was considered to be one nearly everywhere else. Shooting fish with firearms is now illegal in many countries, so the market for the guns dried up.