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Pneumatic Speargun Piston Sticking: how to overcome it

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popgun pete

Well-Known Member
Jul 30, 2008
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After some weeks of not being used pneumatic speargun pistons often refuse to budge at first when you try to muzzle load your gun. With the piston failing to move the spear tail is now firmly stuck in the piston which can only be jerked out with some difficulty. A way around this problem is to push the piston back with the gadget shown here before you next use your pneumatic speargun. They were made by Nemrod and each new pneumatic speargun was originally supplied with them in the sixties and early seventies. The knob on the top of the gadget made pushing down with the palm of your hand easier and if all else failed then you could invert the gun and push it down onto the gadget while pressed against the floor. Ideally a few drips of oil placed into the muzzle opening before commencing pushing is best as when the piston first moves oil runs into the inner barrel surrounding the piston nose which adds to lubrication of the piston and the front section of the inner barrel. In early Nemrod pneumatic guns the muzzle relief port holes were in the wrong place, they were at the front of the muzzle instead of the rear, so this gadget was essential to preventing the pistons corroding and seizing up.
Nemrod plunger R.jpg

Note that the gadget's rounded nose prevents it from jamming in the piston face, so you don't have the problem of a spear tail being stuck in the gun.
 
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After some weeks of not being used pneumatic speargun pistons often refuse to budge at first when you try to muzzle load your gun. With the piston failing to move the spear tail is now firmly stuck in the piston which can only be jerked out with some difficulty. A way around this problem is to push the piston back with the gadget shown here before you next use your pneumatic speargun. They were made by Nemrod and each new pneumatic speargun was originally supplied with them in the sixties and early seventies. The knob on the top of the gadget made pushing down with the palm of your hand easier and if all else failed then you could invert the gun and push it down onto the gadget while pressed against the floor. Ideally a few drips of oil placed into the muzzle opening before commencing pushing is best as when the piston first moves oil runs into the inner barrel surrounding the piston nose which adds to lubrication of the piston and the front section of the inner barrel. In early Nemrod pneumatic guns the muzzle relief port holes were in the wrong place, they were at the front of the muzzle instead of the rear, so this gadget was essential to preventing the pistons corroding and seizing up.
View attachment 53597
Note that the gadget's rounded nose prevents it from jamming in the piston face, so you don't have the problem of a spear tail being stuck in the gun.
Or keep the gun oiled with some 3&1 oil in the end after each use!
 
Or keep the gun oiled with some 3&1 oil in the end after each use!
Unless the gun has muzzle relief ports, in which case oil can be introduced in through the side ports, the piston clamps onto the shock absorber anvil and the oil cannot get past that unless you push the piston back. In old guns with all-metal pistons the oil could infiltrate through the tiny hydraulic lock eliminator hole in the side of the piston head, but this is absent in modern spearguns. Nemrod guns until the ports were moved from the front to the rear of the muzzle don't access the piston sides at all except for that tiny hole and there was usually some saltwater trapped in there, the reason why Nemrod supplied the green plastic plunger in the first place.
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Here at the top of this photo is the Taimen specIal tool that can be used for this purpose in the Taimen gun.
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A manufacturer has recently expressed interest in this device which was nearly in danger of being completely forgotten, but now I see it as an essential bit of kit which may become available from companies such as LG-Sub as their products are machined from plastic rod stock and they don't incur the expense of an injection mold to try the product out. With the increase in use of pneumovacuum spearguns, which don't have any muzzle relief ports, this gadget will be essential to keeping those guns operating in the long term as the piston must be pushed back to get any lubrication in via the muzzle opening. This issue has been flagged before here: https://forums.deeperblue.com/threads/corrosion-potential-in-vacuum-barrel-guns.91611/#post-960267
 
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