Rationale behind Pneumatic, Pistonless and Pneumovacuum Spearguns

  • There is a simple rationale for the differences between standard pneumatic, pneumovacuum and pistonless pneumatic spearguns. It all has to do with the metal running surface used in, or on, the gun and the likelihood of it being damaged and consequently causing rubber seal wear and pressurized air/oil leaks.

    Standard wet barrel pneumatic speargun

    The standard pneumatic gun’s running surface is the inner barrel tube and being internal it is somewhat protected from the environment of sand and grit which is found on the bottom in most oceanic environments, so it rarely gets into the gun, especially if the gun floats after the shot. Provided the water is clean they can have minimal bore wear even with alloy inner barrels. Guns such as the “Sten” have lasted for decades in regular use.

    Pistonless pneumatic speargun

    The running surface on the pistonless pneumatic gun is the spear shaft itself and it moves through a stationary seal in the gun’s muzzle. The spear flies out and collides with the environment, so it is more likely to run into sand and rocks. As the smooth surface of the spear is critical the spears therefore need to be made of better stuff, such as stainless and spring stainless steel. Now when diving in rivers and lakes the water often contains sand, silt and grit in suspension and that may gain entrance into the gun’s inner barrel when the gun is being muzzled loaded. If it is a standard gun then water is sucked into the inner barrel bore taking anything else in with it. If that is an inevitability then it makes sense to do away with the inner barrel entirely and let the spear take its chances in the environment. It is much easier to inspect a spear for nicks and scratches, unlike an inner barrel bore. Therefore you have guns like the "Vlanik" and "Evolusion" to be used in turbid waters

    Pneumovacuum “dry barrel” speargun

    The pneumovacuum gun has two metal running surfaces, the inner barrel bore and the spear. So why use it? Well in turbid water you can use it to keep suspended material out of the inner barrel bore, as only a small volume is open at the muzzle entrance when the gun is discharged, so that is why you have pneumovacuum guns like the “Taimen” and “Pelengas”, but they have to use good quality spears.

    I could talk about efficiency gains/losses of the various types, but as long as a gun is powerful and you take maybe a dozen or so shots on each dive outing then efficiency will not worry you too much unless the gun is extremely inefficient, such as found with a metal coil spring gun.

  • I should add the LG-Sub Manilu "Revolution" to that list of pneumovacuum guns, as unlike the muzzle held, nozzle type vacuum cuff that runs directly on the spear shaft now used by most others it is in a sense a return to the "Mamba" type system where the line slide or slider is the sealing element for the muzzle. LG-Sub have made a very tiny version which is indistinguishable from a standard line slide unless you take a very close look at it. Another muzzle system is that developed by Tromic in Croatia where the Mamba concept has been reduced to a single "O" ring which, with a range of muzzle variations, is the "Tomba" pneumovacuum system. It provides all the benefits of dry barrel operation in a very simple to install conversion unit and the accompanying line slide centralizes the shaft for "O" ring alignment in the special non-side ported muzzle. All you have to do is buy good quality smooth running surface spears that don’t rust or nick and keep them that way, i.e. take care in cutting fish away from your spear as some dive knives with hard and razor sharp blades can slightly nick your shaft, especially 316 stainless. No such worries with 17-4 PH stainless, but still advisable to be careful with high quality blades as you don't want to ruin the knife edge either. Shooting fish in the skull can bury your tip in places that are hard to pull out or push through, so brain surgery is necessary as you put on your Ben Casey hat. As for the squeamish, well it is just the reality of killing things to eat them, so think of it as part of the job in securing meat for the table.

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