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Old Salvimar Predathor, couldn’t reload after a shot.

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

stefpix

Well-Known Member
Aug 15, 2015
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Hi
I have been using a Salvimar Predathor 65 for 3 years.
today I took it out after some months. I had re pressurized to 20 bar and added some oil with the pump.

today I loaded it ok, but after I speared a fish, there was no way I could reload it. Even with 2 hands, even out of the water using my body weight, the shaft would not move an inch.

when I went home I checked with the gauge, 20 bar. I took much of the air out and I could load it unload it. The piston felt like moving smoothly.

I wonder what would make it impossible to load it after a shot.
I have no experience in taking it apart. I am in the USA where getting parts takes a while.
I have a spare Predathor vuoto 55, the 65 is the basic model.

also I can’t find anywhere if the Predathor plus, the one with the power reg, comes with a plated shaft like the basic model or with a stainless steel shaft like the vuoto.

I love using pneumatics as I can attach a go pro on the tip with a Velcro mount and they are portable and powerful. But there are less maintenance tutorials.
 
To be unable to load the gun after a shot sounds like something had jammed the piston. Whatever it was letting the pressure out enabled the piston to move again. I suggest that you let all the air out, remove the muzzle and pull the piston out and make sure the centre "O" ring has not busted as the rear wiper seal alone can keep air in. You can also see if anything has marked the body of the plastic piston, such as some foreign material that has entered the muzzle. I once fished out a tiny smooth pebble that had got into my gun on the wet side, it never scored the inner barrel fortunately, but had got past the outer wiper seal. Modern guns don’t have forward wiper seals.

Because a lot of purchasers buy on price manufacturers don't put their highest specification parts in their guns as standard. The only reason stainless shafts go in the Vuoto guns is because a smooth shaft surface is critical to the life of the vacuum seal in those guns. Inox shafts tend to go in the upmarket models, but it also depends on who packed the guns at the factory and what they have available at the time. Long thin shafts are usually spring stainless to resist bending during muzzle loading, whereas short shafts being hard to bend are usually plated steel.
 
Reactions: stefpix
Thank you. Are you aware of any website that shows how to take a predathor apart? If something busted, what parts would I need to change?
i see there is a shock absorber part for sale, I wonder if that could be the culprit,
 
All you need to do is push the piston back, pass a rod or Phillips head screwdriver blade through opposing muzzle ports and unscrew the muzzle using the rod as a wrench. You then pull the piston out. The shock absorber is in the removed muzzle which you can check out at the same time. While the gun is opened up you can change the oil. Spare parts are available on line if you search.

Check the inner barrel bore for scratches with a flashlight.
 
Hi thank you. I removed the muzzle. I could take the piston out. It feels like there is some gunk on the front part of the piston, in front of the O rings.
I can not remove the shock absorber. Maybe I can rinse the muzzle. It looks like there are some scratches in the inner barrel. But it never leaked air.
Is it worth fixing? Piston replacement I could get. But I am not sure if I am confident to take the trigger mech and rear handle apart.
I can upload photos tomorrow with daylight it is easier to show the details.
at the tip of the inner barrel there is a small spot that looks oxidized.
I can find a new gun for 90 usd plush shipping. But I dislike the idea of producing unnecessary waste from something that can be fixed.
is it normal that debris can accumulate on the front part of the piston?
 
Problems can occur if a cocked gun is dropped to the bottom as then sand can enter the gun via the muzzle ports. Usually this sand gets blown out with the next shot, but it can cause damage if the sand embeds in the piston. Scratches forward of the area swept by the piston seals don't cause problems. Whenever I had to place a loaded gun on the bottom I either parked it on a sheet of broken kelp or drove the tip into the bottom leaving the gun to stand vertical, but this is no good in any surge or current.
 
Reactions: Pinniped72 and stefpix
It makes sense. Do you think it may be worth replacing the piston? If it did not leak air the seals should be good even with those minor scratches.
I saw there is a salvimar kit race. Can I change the piston with the race piston without replacing the trigger mech?
the price difference between the reg piston and race kit is minimal.
I could also get a vuoto muzzle kit to minimize the intake of debris.
I guess every winter it may be good to take the muzzle and piston apart and clean it.
Can I rinse the inner barrel with fresh water and let it dry for some days?
I know with the standard non stainless shaft the slider bushing sometimes would rust a little (even if rinsed in fresh water after each day) and would make loading a lot harder. So I imagine a little grit in the barrel will make it hard.
 
You can use a magnifying glass to check for any sand/grit particles embedded in the piston and then use a pin or needle to pick any out. Rubbing your fingertips along a dry piston will detect any roughness as you will feel any bumps. If the gun does not leak air then I suggest that you don’t change anything except the oil. Check the removed oil by draining it into a container where you can examine if anything foreign is in it. I use a glass jar or whatever glass item comes to hand as the oil is easily washed out in warm soapy water afterwards.
 
Note that a piece of grit trapped between your shaft's metal stop ring and the shaft can jam the shaft and prevent loading as the stop ring cannot slide on the shaft. Rare, but it can happen.
 
I already drained the oil in an empty can of beans.
the piston definitely looks scratched in front of the o rings. And there is a little brown on the metal ring on the piston.
I could wash the interior of the barrel, the piston and reassemble in a coupe, of days. The rear of the piston looks like it has no scratches.
I have 2 spare guns, so I am in no rush.
the sand can come in when I end my dive. I unload the gun and wind my floatline around the buoy while standing in shallow water.
I touched the o rings. I wonder if they need replacements. A new piston is $8 so not a big deal.
I tried to rub with a q tip the brown spot at the front of the inner barrel, maybe 1 cm from the end,, but it does not come off.
 
Sand at the end of the dive causes no problems as it just washes out. It is when the piston is travelling during cocking and shooting that causes sand to drag against the metal of the barrel. Anodizing (aluminium oxide, think of sapphires) is hard, but quartz is harder and with the piston as a rubbing block it can penetrate the anodizing. The alloy thus exposed then goes grey with corrosion. If conditions are too arduous then you need a stainless steel inner barrel such as the Pelengas spearguns use. Diving in rivers and lakes can be rather gritty and that is why Russian and Ukrainian guns use stainless steel inner barrels, but then you have to watch out for saltwater corrosion as stainless steel will corrode under the right conditions. Thorough freshwater cleaning of guns after diving keeps such problems at bay.
 
Reactions: stefpix
Ps. I have had it for 4 years, never taken it apart. Good lesson
thanks. I may orde a couple of pistons, some oil and some other stuff, to have as a spare. Do you think the barrel with some scratches may last a few more years? I had been using this since 2017. Proponents of band guns state the ease of maintenance.
I guess if I inspected the piston every year less grit would have accumulated.
is the kit race piston a worth upgrade and compatible with the trigger mech the gun comes with?
 
The Race kit is not really worth buying. I bought one and never used it, although my aim was for the green trigger and line release arm and safety slide button. Rather than pull the gun apart I may install it at a later date in my Predathor “Vuoto” 100. The piston seals can accommodate slight scratches, so you should still get more use out of the gun. A long continuous scratch is what causes problems and the gun will leak air noticeably in the water, unless that happens you should be OK. I always soak my guns in a plastic rubbish bin full of water after a dive, the rubbish bin transports my wetsuit and dive boots and sits in the back of my wagon. Everything gets hosed off before they go in the tub to minimize sand getting into the tub, although you always get a few grains that sink to the bottom.
 
Thank you so much for your help. I soak the gun in the bath tub each time. I don't have an outdoor space.
I ordered the Race kit and a couple of spare pistons. The price was lower than spare bands for band guns, I feel it is good to have some spares. What do you mean by: "Rather than pull the gun apart I may install it at a later date in my Predathor “Vuoto” 100"? don't you have to take the Vuoto apart anyway? I may just use the green piston, without replacing the other parts. Maybe it is made of better plastic that collects less sand

Anyway, here are the photos of the piston. pretty damaged. Corrosion is mostly in the front but slowly getting in the rear part. I feel i need to install a brand new piston. I have used this from 2017, never opened it. SO it it the 5th year.
Maybe it is worth changing the piston every year or 2.
Is it ok to fill the inner barrel with fresh water and let it sit? maybe use some dish soap to remove the old oil, rinse, dry, oil, replace the piston.
 

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I don't think of removing the muzzle as taking the gun apart. Knocking pins out and undoing parts at the back end does qualify. Over the years Salvimar has changed the Race kit piston, this one was purchased in late 2018. I think the ringbarked green pistons were prone to snapping as over the years the annular groove became progressively shallower. Now all you get is different colour “O” rings and cone seal!

Washing the gun interior using water will send water into the tank if you pour it down the open muzzle, so I don’t recommend it. To clean the gun internally you really need to pull the nose cone off, then whatever you pour in will tip out and the gun can dry off. Ideally the tank should be removed as well.

Original version below.
 
Last edited:
That piston is pretty chewed up which shows how much sand has been sitting in the muzzle when you used the gun. Pneumatic guns really need to stay off the bottom and that is why floating after the shot guns were such a boon. If I really need to put my gun down and there is nowhere to stash it over a sandy bottom then I will execute a low power shot and let the gun float anchored by its shaft sitting on the bottom. Reloading after a low power shot is not such a chore if the gun is highly pressurised, I always use the maximum that I can load against without turning myself inside out.
 
Do you think that by removing the piston I got rid of any sand in the barrel?
maybe the advantage of the plastic piston is that it gets scratched more than the aluminum barrel would.
i attach a GoPro on the barrel so the gun does not float much.
since this is the 5th year I used this speargun, which was $90 it seems still good. From now on I will open the front in the winter and replace the oil every year. Maybe the piston yearly or every other year.
I will check the vuoto 55 I have. I want to see if the sealed muzzle limits the accumulation of sand.
 
As I doubt any sand got past the second "O" ring there should be no sand in the gun once you pulled the piston out. A bit of saltwater got past the first "O" ring and rusted the metal, but that is nothing to worry about as the rust did not grow. On the plus side you can see the guns still work even with neglect, but changing the oil every two years is recommended and yearly for heavy use, that was how it used to be with the original pneumatic guns.

When you shoot a vacuum barrel gun as the spear departs the muzzle water rushes back into the muzzle interior, so in sandy conditions some suspended particles may go in with the inflow, but swinging the gun around before loading should shake it out. However you cannot really see what is going on with a vacuum muzzle gun unless you unscrew the muzzle whereas with a wet barrel gun you can look in the port holes and check the piston for scratches. Especially now the port holes are so big.
 
It is a good lesson, after all I got use from this gun. I will probably maintain it more. Keep some spare parts on hand.
the grit/sand on the piston felt quite fine.
I saw in that salvimar vuoto video that it is best to unscrew the dry muzzle and rinse it and grease the threads each time. Sometimes when I left the gun on the seabed attached to the float it got dragged. I mostly go spearfishing where the Atlantic Ocean meets the New York bay, and the tidal current can be really strong by the inlets. It is what it is.
this incident and your help helped me learn how to take better care.
there is a place in Florida where for $65 and up they service pneumatics and change all the o rings. It may be worth once in a while. I ammwait for the piston (got race and regular), also ordered a dry muzzle so I have both options.
I have the 55 vuoto which I like, but I find the 8mm shaft of the basic version has more punch.
at the end the servicing parts are cheaper than the 20 dollars for new bands for the band guns that get replaced every year.
 
Most Salvimar users change the original piston and shock absorber by Mares. Apparently, they are better quality.
 
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