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Pneumatic dismantling: how to get inside

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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leegirl

Member
Jun 11, 2013
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thanks, ill try its just that i have no reciept it was on sale and dont like my chances :(
 
popgun pete

popgun pete

Well-Known Member
Jul 30, 2008
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thanks, ill try its just that i have no reciept it was on sale and dont like my chances :(

I doubt that they sell too many of those guns in a week, so they should remember the purchase. Plus they may have recorded the gun's serial number in their stock inventory book.
 
S

spoolin01

Well-Known Member
May 20, 2008
38
4
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They are all very similar in construction, the only inner barrel that cannot turn is in the Scubapro "Magnum" as the sear pivot pin in that gun projects well outside the inner barrel tubing and engages in long slots on either side of the handle molding. To turn the inner barrel you would have to bend the ends of the pivot pin or break the molding, both are reasonably substantial in construction. Having damaged guns through ignorance I learned by my mistakes, that is where this information all comes from, it is the product of experience, not theory....
Same with Seac Sub Asso. Sear pin appears to be same dimensions as trigger pivot pin.
 
Diving Gecko

Diving Gecko

shooter & shooter
Jun 24, 2008
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I actually just did quite a number of pics as I put together my gun after a barrel mod.
Perhaps it can help someone about to take theirs apart.
Just reverse the sequence but remember to take the air out and think about how and where to empty the oil.
Also, remember to take out the trigger pin before you try to pull the inner barrel out of the handle - if you don't, you risk bending the pin!

Here's a boring, but hopefully informative slideshow:



This is a Seac Hunter and it is virtually identical to the Asso and likely very close to the Cressi and others.
 
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Diving Gecko

Diving Gecko

shooter & shooter
Jun 24, 2008
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They are all very similar in construction, the only inner barrel that cannot turn is in the Scubapro "Magnum" as the sear pivot pin in that gun projects well outside the inner barrel tubing and engages in long slots on either side of the handle molding. To turn the inner barrel you would have to bend the ends of the pivot pin or break the molding, both are reasonably substantial in construction. Having damaged guns through ignorance I learned by my mistakes, that is where this information all comes from, it is the product of experience, not theory.

I have now added a thread on the main cause of tight to remove muzzles: http://forums.deeperblue.com/pneumatic-spearguns/95063-alert-dry-vacuum-barrel-kit-users.html. This advice is also extended to oil change muzzle removal operations.

The feature of extending the sear pivot pin to stop rotating handles is not surprisingly also in the Predathor guns and it's one of the best features of that handle in term of servicing. I say "not surprisingly" as your historic sense of these things has helped us recognize that Salvimar's Vintair line of guns is basically the Magnum guns in new disguise and the Predathor is a facelifted/upgraded line of those guns.

Actually, the Seac Hunter has it, too. But that handle has a thinner wall thickness with rails extending towards the barrel doing the job, and I have actually managed to turn the pivot pin straight through those rails, so the feature doesn't work as well on that gun. However, on the Predathor handle there's a lot less air space with much, much thicker sidewalls. It's more like the grooves for the pivot pin are slots in much thicker body resulting in a more sturdy design where the pin can't wreck its way through the plastic.
 
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popgun pete

popgun pete

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Jul 30, 2008
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The Scubapro "Magnum" was created by the same people who did the Mares guns and who were given a design brief to make a gun superior in construction to anything else on the market, and that included its assembly methods. Scubapro were known for top quality and prices to match, so the guns had to justify the asking price. The upstream power regulator valve was to increase the transfer port size by having two "Siamese" ports covered by a curved segment, flat rubber seal shaped much like a fruit segment out of an orange. Given the propensity of people twisting the inner barrel with the muzzle thread frozen they designed the long sear pivot pin and rail locating system in the handgrip interior to absolutely stop the inner barrel from turning. An interesting side note is Scubapro wanted to discourage people opening guns up to change the oil, so early guns have staked muzzles to stop the muzzle turning and the guns were grease lubricated. The folly of this idea soon had oil lubrication restored and the muzzles no longer staked. “Staking” means screwing the muzzle on then using a metal punch to “set up” or crease the inner barrel screw thread through one of the muzzle relief ports. Unless you smooth out this intentional damage to the screw thread you cannot unscrew the muzzle and all gun repairs have to proceed via the rear end of the gun.

Speaking of repairs from the rear end of a pneumatic gun here is the link to the tube spanner thread and other tools that can be used to undo the inlet valve body: .https://forums.deeperblue.com/threads/diy-tool-for-removing-rear-inlet-valve.93638/#post-870311
 
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W

WilliG

New Member
Jan 19, 2021
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Sometimes a pneumatic speargun will be difficult to disassemble easily because the parts are a tight fit (like in a Mares "Mirage"!). I have found this method useful on most rear handle pneumatic models.

First release all the air with any power selector set to "maximum" as this ensures that all the air chambers in the gun are connected to each other, that way you will not leave any compressed air inside the gun. Then take the spear or a blunt ended rod of similar diameter and push the piston back so that it just disappears into the inner barrel and leaves a clear view through the muzzle's relief ports. Using a metal rod, or a screwdriver that is a reasonably close fit in the relief ports, pass it through opposing relief ports to provide a handle whereby you can unscrew the muzzle by hanging onto each end of the rod or screwdriver (round shaft Phillips head type, not a blade tip screwdriver). Sitting down on a chair you can trap the grip handle between your feet as you apply a twisting torque to undo the muzzle while holding the gun vertical between your knees. Generally the muzzle will come off easily after only a few turns, so you can unscrew it the rest of the way with your fingers. Put some fresh grease on the exposed muzzle threads and then screw the muzzle back on. When the muzzle contacts the nose cone, you will feel the muzzle stop turning, back the muzzle off a number of turns to leave a gap. Now take the gun's handpump and screw it into the rear of the gun. With the muzzle pointed downwards and resting on a rubber surface like an old thong (the "flip-flop" footwear type) begin pumping using slow strokes and watch the muzzle nose cone. A small amount of air pressure in the gun will cause the nose cone to slide down the inner barrel tube and out of the tank, the reason that you only unscrewed the muzzle by three or four turns was to make sure that the nose cone did not come right out of the tank or you would have oil everywhere, plus you want the piston to stay in the inner barrel bore without the piston seals emerging for the exact same reason.

Now remove the handpump and release any air from the gun as before, there will be very little pressure with only a small number of pump strokes. Unscrew the muzzle and remove it, then twist and pull the nose cone and slide it up over the inner barrel threads. You will find that the "O" ring on the inner barrel tube has chased the nose cone part way up the inner barrel threads, that is why you greased them earlier. Make sure that the nose cone has its outer "O" ring, sometimes it falls off and will be inside the tank, in which case you will need to retrieve it later. Pull the piston out of the inner barrel and up end the gun over a clean container like a glass screw top pickle jar to collect the oil. Leave it for a while to fully drain the oil out of the gun, then return the gun to the barrel up position and screw the muzzle back on to about half distance on the screw threads. Now hold the gun by the front of the tank in one hand and strike the muzzle nose with a soft faced hammer (preferably a nylon faced, double sided hammer like a "Thor", that is what I use). A few good hits and the barrel and handle will drop out of the tank tube, make sure that it does not have too far to fall and then the rear of the muzzle will not hit the front end of the tank. I hold the gun just clear of the floor with a rubber thong directly underneath the grip for the back of the handle to fall down onto, that way there will be no damage to anything. Unscrew the muzzle, put it to one side and carefully lift the tank clear of the inner barrel and place the tank on a level table or bench surface with something resting against the tank to stop it rolling off and falling onto the floor. Modern speargun tanks are light and roll very easily!

Find somewhere clean to place the very oily inner barrel, power regular block and rear handle assembly. Now you can see all the inner "works" and can carry out whatever you had to do which required getting inside the gun. A large plastic laundry bucket makes a good container to sit the dismantled gun in, you can buy inexpensive ones and just use them for your speargun work, that way it will offer a clean container which is easily washed out afterwards to remove any oil. If you cap the glass jar then you can re-use the oil poured out of the gun, especially if it is very clean and has no obvious contamination.

If you want the tank tube to line up in the same position as before with respect to rotation on the gun (for sticker alignment) then mark the front sight position on the nose cone end of the tank tube with some adhesive tape and do the same for the rear end adjacent to the rear sights on top of the grip handle. Putting the gun together push the tank on with the rear end correctly lined up as it is often hard to twist the tank around afterwards due to the two or three main body "O" rings at that end of the gun. It is a different story with the nose cone as once pushed on you can line it up by twisting it. Remember to tip the oil back into the gun before replacing the nose cone, then screw the muzzle back on and you are ready to re-pressurize the gun.

Use clean newspaper to make a temporary work surface (floor and bench top) that will catch any spilt oil and have some cloth rags for wiping parts clean, cotton garments that have worn out make good rags as they are lint free as they have lost most of their surface fuzz, hence are as the saying goes, "threadbare". Do the work where you will not have any dust or dirt blowing around as the oily parts attract such things like a magnet and then you will have to wipe everything clean of any oil before reassembling the gun. With pneumatic speargun maintenance cleanliness is everything as seals are unforgiving of contaminants getting between them and the seating surfaces they sit on or abut against.
Thanks Pete, an old thread but handy ,have a reef 70 and 92 I used a lot in the 90s that I've dusted off and intend on using again, they need a bit of attention and the maintenance info has been handy.
Cheers
 
Stamatis

Stamatis

Active Member
Aug 29, 2017
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Hello! Since this is a thread dedicated to service-related issues, I thought I might as well ask something here:

I noticed diminished performance from my Savli Vuoto 100, so I decided that a change of oil is in order.
I got the piston out and there is some murk on it, and I wonder what it means
Also, after cleaning it up, I noticed that 2 ring-like metal parts look slightly decolorized, meaning that slight corrosion has occurred. It is nothing enough that calls for replacement, but it is there.
So what are the appropriate actions now?
Cheers!
 

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popgun pete

popgun pete

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Jul 30, 2008
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Reduction in performance will not be caused by the oil, but what has probably happened is the vacuum muzzle seal has been leaking and water gets sucked into the barrel. The effort to push this water out during the shot acts as a brake as the gun has no muzzle relief ports. Also some water can be forced past the piston seals and has corroded the metal piston, but not too much as the piston tail itself looks rust free. Change the gun's oil and put the discarded oil in a glass and see if water settles out on the bottom. Install a new muzzle vacuum seal and the performance should return.
 
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Stamatis

Stamatis

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Reduction in performance will not be caused by the oil, but what has probably happened is the vacuum muzzle seal has been leaking and water gets sucked into the barrel. The effort to push this water out during the shot acts as a brake as the gun has no muzzle relief ports. Also some water can be forced past the piston seals and has corroded the metal piston, but not too much as the piston tail itself looks rust free. Change the gun's oil and put the discarded oil in a glass and see if water settles out on the bottom. Install a new muzzle vacuum seal and the performance should return.
Thanks for the quick response!

I don't see much oil dripping from the barrel tube, which is really weird! It's a very small quantity and it is murky! How is it possible?

I can see some corrosion in the inner barrel as well, probably in the spot were the piston was

The vacuum seal looks still great visually, but maybe I should replace it just in case
 
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popgun pete

popgun pete

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In order to drain oil from the gun you need to take the nose cone off after removing the muzzle. A lot of the oil is in the tank tube and the power regulator bulkhead prevents it from running out of the inner barrel with just it being open. The alloy barrel should not have corroded.
 
Stamatis

Stamatis

Active Member
Aug 29, 2017
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In order to drain oil from the gun you need to take the nose cone off after removing the muzzle. A lot of the oil is in the tank tube and the power regulator bulkhead prevents it from running out of the inner barrel with just it being open. The alloy barrel should not have corroded.
Ι am afraid a bit of corrosion does exist in the inner barrel, so some sea water definitely was there. I tried to clean the rust, and I could feel a slight notch there. I am hoping this won't cause an issue because there was no air leak, not a noticeable one.
IMG 20211127 221207
 
popgun pete

popgun pete

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Jul 30, 2008
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Did you get all the old oil out as there should have been more than a few drops? The Predathor 100 cm guns contain 45 ml of oil. That rust has just been transferred to the barrel surface from the piston, it has stuck there like paint. It should rub off, but as you don't want to scratch through the barrel anodising I think unless it can be moved using a wooden or plastic toothpick that you can just leave it. Because the piston sits there when the gun is not used it has been able to build up. Also as I pointed out some time ago water can sit around the piston nose even if the gun has no problems as there is no way out unless you periodically push the piston back with the muzzle pointed downwards to let saltwater out and flush the area with freshwater.

 
Stamatis

Stamatis

Active Member
Aug 29, 2017
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Did you get all the old oil out as there should have been more than a few drops? The Predathor 100 cm guns contain 45 ml of oil. That rust has just been transferred to the barrel surface from the piston, it has stuck there like paint. It should rub off, but as you don't want to scratch through the barrel anodising I think unless it can be moved using a wooden or plastic toothpick that you can just leave it. Because the piston sits there when the gun is not used it has been able to build up. Also as I pointed out some time ago water can sit around the piston nose even if the gun has no problems as there is no way out unless you periodically push the piston back with the muzzle pointed downwards to let saltwater out and flush the area with freshwater.

Is there a chance that the oil escapes from the piston and out the barrel?
I am sure I got all the old oil out, and it was really no more than 10ml (and really murky).
I feel that I should probably make sure none of it is left inside the gun because it might cause damage eventually.
That previous post is really intuitive, thank you! I wish I had noticed it before!!!
Thinking out loud: RIsinng a100 gun at 20atm will be tricky outside the sea because of the force required to charge it. One solution would be to make the 'exit' shot with the power reducer set to low so that the situation is more manageable, but this is not ideal. Or I could use the shaft of my (30y) old small Asso 30!
 
popgun pete

popgun pete

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Jul 30, 2008
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Pushing the piston back just a few centimetres is all you need to do as the front of the piston has to disengage from the shock absorber anvil face which otherwise is creating a seal keeping trapped water in around the nose of the piston. This is only a problem on vacuum barrel guns, muzzle relief ports in standard guns allow water to circulate in this location as they sit just behind the anvil impact face.

Possibly the oil in your gun was not the correct amount from the factory. When guns leak oil they also leak air and you cannot miss it as the gun soon becomes covered in oil around the area of the leak. Sometimes in a store someone will check the air by pushing in the inlet valve which if they have not stood the gun on its nose some time before doing it results in oil blasting out of the gun and being lost, but then they don't bother to replace it. That can result in a gun being low on oil, the amount of oil increases as guns get longer to provide enough for coverage of the internal surfaces and leave some of it to slosh around freely. The amount of oil is not super critical, a few ml either way is not going to cause problems unless a gun is very short or has a very small volume tank, then oil will steal tank capacity needed for compressed air if you use too much oil.
 
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Stamatis

Stamatis

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Aug 29, 2017
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Pushing the piston back just a few centimetres is all you need to do as the front of the piston has to disengage from the shock absorber anvil face which otherwise is creating a seal keeping trapped water in around the nose of the piston. This is only a problem on vacuum barrel guns, muzzle relief ports in standard guns allow water to circulate in this location as they sit just behind the anvil impact face.

Possibly the oil in your gun was not the correct amount from the factory. When guns leak oil they also leak air and you cannot miss it as the gun soon becomes covered in oil around the area of the leak. Sometimes in a store someone will check the air by pushing in the inlet valve which if they have not stood the gun on its nose some time before doing it results in oil blasting out of the gun and being lost, but then they don't bother to replace it. That can result in a gun being low on oil, the amount of oil increases as guns get longer to provide enough for coverage of the internal surfaces and leave some of it to slosh around freely. The amount of oil is not super critical, a few ml either way is not going to cause problems unless a gun is very short or has a very small volume tank, then oil will steal tank capacity needed for compressed air if you use too much oil.
Ι think I am covered now, thank you so much for your time and info!
 
Stamatis

Stamatis

Active Member
Aug 29, 2017
122
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Did you get all the old oil out as there should have been more than a few drops? The Predathor 100 cm guns contain 45 ml of oil. That rust has just been transferred to the barrel surface from the piston, it has stuck there like paint. It should rub off, but as you don't want to scratch through the barrel anodising I think unless it can be moved using a wooden or plastic toothpick that you can just leave it. Because the piston sits there when the gun is not used it has been able to build up. Also as I pointed out some time ago water can sit around the piston nose even if the gun has no problems as there is no way out unless you periodically push the piston back with the muzzle pointed downwards to let saltwater out and flush the area with freshwater.

Hello again!
I am getting ready for summer vacation, which of course includes speargun gear check!
I tried to rub off the rust unsuccessfully, so I left it and see what happens. I only used the gun once after changing the oil, and I was not happy with the power performance, which made me concerned.
Today I did some dry testing after adding some pressure the piston was stuck at first, and I had to let some air out. After that, it worked as expected, and I even added the pressure back without an issue (This whole thing was weird). I can feel on my hand that the piston is bumping somewhere on its way up or down near the exit, most likely at the point where the tube is rusty.
I am concerned that the rust disrupts the piston's 'momentum', and that it will eventually damage the piston seals.
Not sure if anyone can make anything out of my observations though. :)
 
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