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Salvimar piston replacement options

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Active Member
Sep 8, 2016
Does anyone make an aftermarket piston that doesnt suck? I go thru about 2-3 pistons a year that fail at the worst times ha. The salvimar (vuoto) ones just seem like such cheap crap plastic. And no my gun is not over pressurized, and i dont take short rock shots that jam the spear into the piston. Theres gotta be someone out there turning some stronger stuff no?
Try LG-Sub, but I don't think the problem is with the Salvimar piston, something else could be wrong. There could be a problem with the shock absorber, like its rubber rings have busted.
Salvimar vacuum muzzle.jpg

Note the above photo was from before the Vuoto guns went on sale, so it has a metal shock absorber and was probably a pre-production prototype.

What the shock absorbers are like now.
Salvimar shock absorber components 2023.jpg

The bore hole in the shock absorbers has to be slightly larger than the diameter of the spear tail stop, thus for 7 mm shafts which have 8 mm diameter tail stops and 8 mm shafts which have 9 mm diameter tail stops. The bores need a small amount of clearance so that the shaft tail stop does not clip the shock absorber anvil on the way out of the gun.
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At one time the shock absorber damper was a rubber sleeve and they are more reliable in my opinion. Mares have always used a rubber sleeve as the damper or shock absorbing element. Part 2 on the diagram below.
Sten Competition Line parts diagram.jpg
Will no more when i open it up but last two times there was nothing wrong with the rings. Oddly on the “white” salvimar pneumatics the shock absorber is just like in the diagram, the sleeve, but ive had those eventually go too.
Will no more when i open it up but last two times there was nothing wrong with the rings. Oddly on the “white” salvimar pneumatics the shock absorber is just like in the diagram, the sleeve, but ive had those eventually go too.
My Mares Sten and my Scubapro Magnum have never given me any trouble and I have put hundreds if not thousands of shots through them. I suspect that plastic parts are not long term compatible with vacuum barrel operation. These two old model guns have metal everything, bar the end bulkheads. Ditto for the Cressi SL70.
muzzles R.jpg

grip rear view R.jpg
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You could search out a Scubapro Magnum piston and shock absorber anvil, they are made of stainless steel and should fit as the Salvimar is basically the same gun.
Magnum L Vintair Plus R.jpg

The Predathor is just a handle shape rejig and a new windmill style side mounted line release of the same gun, i.e. the Vintair. That latter gun with a different rear cap is just the old Magnum.
Scubapro Magnum piston.JPG
Magnum exploded parts.jpg
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Any images of your busted parts? Sometimes the pattern of damage tells the story, if you know what to look for.
Actually pretty confused as to what happened: piston,shock absorber, and all o rings look fine but gun lost most of its air pressure (lil 2 seconds worth came out when depressing the valve before breakdown)
Well the only way to find a leak is pump the gun up to a reasonable pressure and put it in a tub of water and watch where bubbles come out. The leaks can be slow, but if you weight the gun so it stays under and put a drop of detergent in the water froth will form above the leak on the surface, but not instantaneously. That is the race piston, I have one of those but never used it. Carbon black strengthens rubber, coloured rubber is weaker, I know because I worked in the rubber industry for nine years. Now that is a Darkside tank, just might be a crack somewhere is letting air out as after all it is a resin tank tube with reinforcement of carbon fibre. Do the leak test and we will see what comes next.
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The leak points for a pneumatic speargun of the Sten and its clones from other companies are not that many. The places where seals have movement are the most common, which are the piston rings, the power control selector shaft ring and the trigger transmission pin ring. Rarely unless you disturbed it or got some foreign substance lodged in it is the inlet valve "O" ring that serves as the valve seat. Another ring that can leak due to damage during repair work or a faulty installation is the nose cone to inner barrel "O" ring that can be damaged when sliding it over the nose end screw threads on the inner barrel.
Typical O-ring air leak points.jpg
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While it is possible that pistons have been replaced when they were not the source of the air leaks it is possible to add more damping by adding a damping element into the piston to decrease its susceptibility to impact damage. The Russian Taimen gun originally had virtually all of its shock absorption in the polyurethane bush on the nose of the piston and only in later versions was a second polyurethane bush added to the muzzle itself. In post number 6 above the polyurethane elements are shown in orange, but they are not necessarily that colour and the muzzle bush is a grey colour in the sectioned gun photo as can be seen below.
Taimen muzzle section annotated.jpg
A nylon piston could have a central spine that did the pushing of the spear tail being basically a forward continuation of the piston tail. A nylon body would carry the piston seals as usual, but an additional nylon section spaced apart from the piston body could have a rubber or polyurethane bush inserted in between. This would almost be an analog of the early Technisub pistons, where the damping element on the piston nose was a coil spring and from memory there was no damper on the muzzle itself. By today's standards these guns are weak, using up to 20 bar, modern guns can use up to 30 bar.
technisub jaguar piston.jpg

There are two springs as these guns had a ball ended spear tail, a capture device with small balls grabbed the spear tail and held it until the piston nose hit the muzzle stop, the piston nose then telescoped rearwards and freed the spear tail. At times it also lost the locking balls as well and your gun was then out of action. A plastic variation for modern pneumatic spearguns is shown below.
shock absorber piston.jpg

Note the metal tip would have to do the spear pushing as we don't want shaft acceleration to collapse the new piston shock absorber. So while the usual taper on the spear tail held the spear in the gun on the piston nose's tapered entrance, as soon as the piston moves the metal spine extension would be driving the shaft,
piston pushing.jpg
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Turns out it was a small gash in the darkside carbon fiber barrel ☹️. Looks like it was too close to a dive weight
Turns out it was a small gash in the darkside carbon fiber barrel ☹️. Looks like it was too close to a dive weight
Well it is good you found it, the biggest part of solving any problem is to narrow it down to a cause. Maybe you can repair the CF tank, but if not I suggest you switch it to an alloy one, far less trouble.

Tanks are for sale on eBay, you just need the right length. These Cyrano tanks are made of the same tubing everyone uses, but you can either find one the right size or have a longer one shortened in a lathe to cut the tubing off square to the tank axis.
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