Aquatech Black Sea hydropneumatic gun

[popgun pete]

Just reassembling my "Black Sea" gun to ensure that it still works after being laid up over the off-season (it does!). The bucket of water is used to fill the hydropump by submerging the rear of the gun so that the ring of inlet ports on the hydropump body are below the water level in the bucket as shown here. Pumping action takes place by swinging the pump handle outwards, so you do it after lifting the gun clear of the bucket. A "dummy shot" sends a blast of water out of the gun, naturally the gun is never tested on land with a spear inserted in the barrel! I always remove the parts of the hydraulic releasing or firing valve in the rear of the gun and the complete hydropump system over the storage period to allow the gun to completely dry out. Everything is put back together with a coating of light oil for lubrication prior to water entering the gun's internal passages, so that is why there is a slight oil slick on the surface of the water in the bucket.

 

[popgun pete]

A later model of the "Black Sea" gun is offered for sale here http://forums.deeperblue.com/goods-...-sea-1000x9-made-aquatech-s-f-kravchenko.html by a forum member in Italy. Note the rear handle is a plastic version and it has a longer hydropump handle to improve leverage when charging the gun for the next shot.

 

[Jegwan]

Hi Pete,
Thanks for all the information on the Black Sea guns. The Italian 1000x9A is now in Denmark
Jégwan

 

[popgun pete]

Hi Pete,
Thanks for all the information on the Black Sea guns. The Italian 1000x9A is now in Denmark
Jégwan

Good luck with the "Black Sea" gun. I suggest you shoot it with both hands on the rear grip at first as there is some recoil if you use all the power. I have never been brave enough to try shooting my gun with one hand as the rear hydropump pivot bar is stainless steel and I would not want it hitting me in the face, but on your gun this metal pivot bar has been eliminated. After some familiarization shots to get my aim correct (not hard as the spear flies virtually horizontally in a straight line from the gun for about 6 metres) I killed everything that I aimed the gun at which could be carefully lined up, which was an outstanding result for a new gun on its first outing.

It is worth making yourself a short piece of aluminum tube to free the shaft stop ring if it jams, you put the tube over the shaft tail and hit it with the butt of your dive knife and the stop ring will come free as long as you brace the bare threaded spear tip against a hard surface, like a rock (remove the actual spear tip of course). The stop ring going from zero velocity to 45 metres per second (or more) in an instant it tends to be hammered by the shaft tail. By reducing the number of hydropump strokes the gun can be used to shoot smaller specimens at closer range, I use either half the number of strokes or the full complement. Too much power variation and you don't remember how the gun shoots, so stick to a few options with a known set of strokes. Multi-power guns are confusing to use, so selecting two or maybe three options is all that you need. Watch out for other divers, I never use my "Black Sea" gun without checking the whereabouts of other divers as you cock the gun with it laying across your knee while you are working the hydropump lever. If the gun discharges unexpectedly (it should not, but it is better to be safe than sorry) then the shaft will fly off to one side where you would not normally be looking and any resulting accidents will be big ones.

The "Black Sea" gun has a trigger safety of sorts, but don't be tempted into trusting it. I have never used it on my gun as I wrap the shooting line before I charge the gun and the safety is therefore not required as I am in full control of the gun, from the rear end, once charging is completed. If in doubt and a risky situation is developing then just pull the spear free from the charged gun and execute a dummy shot to release the pent up water from the gun. Once out of the gun the spear will not go in again unless this is done.

 

[Jegwan]

Good luck with the "Black Sea" gun. I suggest you shoot it with both hands on the rear grip at first as there is some recoil if you use all the power. I have never been brave enough to try shooting my gun with one hand as the rear hydropump pivot bar is stainless steel and I would not want it hitting me in the face, but on your gun this metal pivot bar has been eliminated. After some familiarization shots to get my aim correct (not hard as the spear flies virtually horizontally in a straight line from the gun for about 6 metres) I killed everything that I aimed the gun at which could be carefully lined up, which was an outstanding result for a new gun on its first outing.

It is worth making yourself a short piece of aluminum tube to free the shaft stop ring if it jams, you put the tube over the shaft tail and hit it with the butt of your dive knife and the stop ring will come free as long as you brace the bare threaded spear tip against a hard surface, like a rock (remove the actual spear tip of course). The stop ring going from zero velocity to 45 metres per second (or more) in an instant it tends to be hammered by the shaft tail. By reducing the number of hydropump strokes the gun can be used to shoot smaller specimens at closer range, I use either half the number of strokes or the full complement. Too much power variation and you don't remember how the gun shoots, so stick to a few options with a known set of strokes. Multi-power guns are confusing to use, so selecting two or maybe three options is all that you need. Watch out for other divers, I never use my "Black Sea" gun without checking the whereabouts of other divers as you cock the gun with it laying across your knee while you are working the hydropump lever. If the gun discharges unexpectedly (it should not, but it is better to be safe than sorry) then the shaft will fly off to one side where you would not normally be looking and any resulting accidents will be big ones.

The "Black Sea" gun has a trigger safety of sorts, but don't be tempted into trusting it. I have never used it on my gun as I wrap the shooting line before I charge the gun and the safety is therefore not required as I am in full control of the gun, from the rear end, once charging is completed. If in doubt and a risky situation is developing then just pull the spear free from the charged gun and execute a dummy shot to release the pent up water from the gun. Once out of the gun the spear will not go in again unless this is done.

Thank you very much for the good advice Pete. I'm at the moment making some small repairs and modifications to the gun. In fact one of the modifications I'm making is a simple system with an O-ring holding the hydropump handle in place when shooting. The handle on my model is bigger then on yours and located on the top of the gun. The handle section of the gun is made of glass fibre reinforced epoxy. I have made a 7mm spear with single flopper for the gun as this is more suitable for the fishing here in Denmark. I will make the a alu tube to free the shaft slide ring - That's a good idea. I'm looking very much forward to test the gun and hope it will be ready for testing before the water here gets to cold. The recoil of the gun sounds amazing.
I will take care and follow your and Sergiy's safety advise.

 

[popgun pete]

The hydropump lever or handle assembly should rotate to the side, it sits on top only for gun transport. When using the gun the lever is then out of the aiming line on the top of the barrel, on my gun it moves to the right hand side. I lay the gun crosswise on my knee with the left hand side facing downwards so that I can work the lever up and down. I am reasonably sure your gun works the same way. The metal band with the slotted piece of plastic that engages the nose end of the hydropump can be rotated on the barrel and that controls the orientation of the pump body once you tighten the band in the new position.

 

[Jegwan]

The hydropump lever or handle assembly should rotate to the side, it sits on top only for gun transport. When using the gun the lever is then out of the aiming line on the top of the barrel, on my gun it moves to the right hand side. I lay the gun crosswise on my knee with the left hand side facing downwards so that I can work the lever up and down. I am reasonably sure your gun works the same way. The metal band with the slotted piece of plastic that engages the nose end of the hydropump can be rotated on the barrel and that controls the orientation of the pump body once you tighten the band in the new position.

My model is different. The hydropump handle is fixed on the top. You have to learn to aim over this or rotate the gun to one side if you don't want it in the aiming line. It is correct that my model uses the same metal band with the slotted piece of plastic as yours, but mine needs to stay on the top as the hydropump handle and the handle section is fixed. See the attached photos. (please note that the trigger and line release plate is taken out of the gun at the moment).

 

[popgun pete]

Well Cammo has a "Black Sea" gun with a similar grey plastic handle and it rotates to the side. You can see his gun, or one like it, in the photo on the Aquatech web-site at the bottom of the page, the "BS1250 x 9A" gun with the titanium body tube. I remember him asking about the hydropump position as his gun arrived with it all disassembled. In the web-site photo the hydropump lever is facing the camera on the right hand side of the gun. Maybe send Cammo a pm to find out for sure.

 

[Jegwan]

Yes. Thats the BS (T) model with 36mm titanium concentric barrel. Mine is the BS (A) model with 30mm aluminium concentric barrel shown above on the Aquatech website. Note the picture that shows that it is possible to complete the gun with different barrel length and handle. That gives the impression that the 30mm aluminium concentric barrel for the "Dnepr" and the "Black Sea" are similar except for the initial working pressure. But I'm not sure if that is correct. In the original Russian text on the site the working pressure of the "Dnepr" is stated to be 60atm and 100atm for the "Black Sea".

 

[popgun pete]

Both "Dnepr" and "Black Sea" spearguns evolved from the same basic unit, but are different guns in that the "Black Sea" speargun was beefed up structurally to take 100 Bar start pressure and its rear removable screw cap was fitted with an elbow tubing connector attaching to the additional hydropump body. It seems odd that the hydropump handle is now on top as in the earliest "Black Sea" guns, which were all 30 mm diameter outer barrels, the hydropump was always positioned on the right hand side of the gun for underwater use. Rotating the rear cap (complete with the elbow connector) on its large screw thread allowed the hydropump body to reposition on the gun and the hydropump's slotted nose end clamp fixed the hydropump in the required orientation. I know this because I remember the discussions that created the "Black Sea" gun in the very first place and one of the main considerations was where to locate the hydropump and its lever handle without it interfering with the aiming of the gun. So it is surprising to learn that this latest version has opted to put the handle on top!

The grey handle with combined grey plastic receiver was created, I guess you could call it the "third generation" model, in order to incorporate the small bore transfer tube of the trigger valve system into the locking chamber's rear cap and not having it radially inserted into the sidewall of the locking chamber where it was located before. That design change made the grip handle, rear cap, small bore transfer tube and trigger valve all one combined unit and it could be unscrewed from the gun as easily as if it was the simple rear cap on the original version of the Aquatech gun. I used to have photos of Cammo's gun in pieces, but they are all on my old computer which no longer boots up, so I cannot check. If the rear cap and transfer tube are fixed in relation to each other then I guess you cannot change it.

On my "Black Sea" gun those two elements are not fixed, so I can put the hydropump on either side, or on top, but the threaded connection stops rotating with the hydropump on the right hand side when the rear connecting boss main thread bottoms out in the rear cap. There is a lot of weight in the back of my "second generation" gun and everything has to be fitted properly before all the handle's twin metal plate sub-frame connecting screws and nuts are tightened up, something that the new integrated handle design eliminated, thus making gun assembly much simpler for the factory.

 

[Jegwan]

Thanks for all the great info Peter.
I have finalized my work on the gun and have tested its functions in my bath top.
The trigger piston do not work as it should. The sealing between this and the barrel is not tight. The seal looks like it is some kind of a nylon washer held by a M5 screw. The trigger piston is made in SS. Is it the same on your gun and have you any experience changing this?
On my Dnepr the trigger piston is made in Aluminium and the seal towards the barrel is an O-ring.

 

[popgun pete]

Thanks for all the great info Peter.
I have finalized my work on the gun and have tested its functions in my bath top.
The trigger piston do not work as it should. The sealing between this and the barrel is not tight. The seal looks like it is some kind of a nylon washer held by a M5 screw. The trigger piston is made in SS. Is it the same on your gun and have you any experience changing this?
On my Dnepr the trigger piston is made in Aluminium and the seal towards the barrel is an O-ring.

My two guns are the same as you describe. I have not had any problems with the "Black Sea" trigger piston, so I have had no reason to change it. I was surprised that it was a nylon washer when I saw it and wondered if the seal was actually the face of the piston shoulder acting on the end of the inner barrel tube. I say this because there are slight scuff marks on the washer, but it still seals. At 1,400 psi plus the seal has to be perfect, so that is why I considered a metal to metal seal, although it seems unlikely.

 

[Jegwan]

My two guns are the same as you describe. I have not had any problems with the "Black Sea" trigger piston, so I have had no reason to change it. I was surprised that it was a nylon washer when I saw it and wondered if the seal was actually the face of the piston shoulder acting on the end of the inner barrel tube. I say this because there are slight scuff marks on the washer, but it still seals. At 1,400 psi plus the seal has to be perfect, so that is why I considered a metal to metal seal, although it seems unlikely.

Ok, thanks Pete. I will make a new nylon washer and hope it solves the problem. I tried using the trigger piston from the Dnepr for a dummy shot. It worked for the loading of the gun but the O-ring is not strong enough to stay in place when the gun is fired. The power of the water column is amazing! I can't wait to see how the gun shoots the spear.​

 

[popgun pete]

Ok, thanks Pete. I will make a new nylon washer and hope it solves the problem. I tried using the trigger piston from the Dnepr for a dummy shot. It worked for the loading of the gun but the O-ring is not strong enough to stay in place when the gun is fired. The power of the water column is amazing! I can't wait to see how the gun shoots the spear.​

Yes, the extremely high pressure extrudes the "O" ring through the gap between the inner barrel bore and the flange on the front of the piston. With one stroke of the hydropump lever 100 Bar pressure instantly is applied to the seal, so a standard rubber "O" ring will not take the pressure as the clearances in that location are too large for that material. A lot of development work went into the high pressure sealing of the "Black Sea" speargun.

 

[Jegwan]

Yes, the extremely high pressure extrudes the "O" ring through the gap between the inner barrel bore and the flange on the front of the piston. With one stroke of the hydropump lever 100 Bar pressure instantly is applied to the seal, so a standard rubber "O" ring will not take the pressure as the clearances in that location are too large for that material. A lot of development work went into the high pressure sealing of the "Black Sea" speargun.

Yes, that I believe. It's a very well engineered gun. I have now machined a new nylon washer. The old washer was quite deformed, so it was a little hard to measure it. I decided to make the new 2.2mm thick, the diameter towards the barrel 8.8mm and the diameter towards the piston 9.3mm with an 15 degree angle. The hole 4.8mm so it would stay in place on the M5 screw. I have added a picture of the new washer. The seal is now tight and everything seems to work as it should.
The cold and windy weather has come to Denmark and the winter is coming, so I cannot try the gun with the new 7mm spear.
I will be in Lombok over Christmas so I will bring the BS and try it there. I have also made a longer 8mm spear with slip tip that hopefully will meet a larger fish out there. I have added a photo of the handle showing the modifications I mentioned earlier.
I have added a bracket for line attachement and the simple O-ring system to keep the hydropump handle in place during transport and diving. I will post my experiences with the Black Sea gun when I'm back from Lombok in January.

 

[popgun pete]

You have done a good job with the washer, it looks like you will be in action soon with the "Black Sea" gun!

 

[Jegwan]

...It is worth making yourself a short piece of aluminum tube to free the shaft stop ring if it jams, you put the tube over the shaft tail and hit it with the butt of your dive knife and the stop ring will come free as long as you brace the bare threaded spear tip against a hard surface, like a rock (remove the actual spear tip of course). The stop ring going from zero velocity to 45 metres per second (or more) in an instant it tends to be hammered by the shaft tail.....

Hi again. While I had access to the lathe, I also made the suggested aluminium tube and some extra spear tail pistons for my Dnepr and Black Sea guns. I have added a photo. This brought my thoughts back to the difference between the guns. The Black Sea spear tail piston is the one to the left with the "fixed" "O"ring. The Dnepr is the one to the right with the "sliding" "O" ring and "relief channel".
I have looked in the Owners O&M manual at the Aquatech webpage. This describe the Black Sea models with a spear tail piston with "sliding" "O" ring and "relief channel". Furthermore shows the drawing http://aquatech1.narod.ru/schematicBlackSea-A.gif of the Black Sea guns that the trigger piston is sealed towards the barrel with an "O" ring like the Dnepr. I guess that we can conclude that this is an error.
What kind of the two spear tail pistons do your guns use and do you have any experience in what difference it does to the performance of the gun using one or the other?

 

[popgun pete]

On the earlier "Aquatech" spear tails manufactured in stainless steel the tail "O" ring slides back and forth a little more than one ring width to either cover or uncover a vent hole drilled through to the rear of the shaft tail via a right angled bend. In the later and much longer brass versions the "O" ring tips over as it sits on a slightly undersized shank, so no need for a drilled hole to provide a vent because once tilted over the "O" ring loses its sealing. When pushed to sit square to the shaft on the groove's front shoulder the "O" ring seals because hydrostatic pressure in the inner barrel helps align it that way. Functionally the two types of spear tails seem to work as well as each other, but the second type of tail is easier to make on a lathe. Plus the brass tail will not damage the inner barrel bore even though the muzzle velocity is very high in the "Black Sea" gun. The web-site drawings are simply schematics, so don't worry too much about them, they just show where the "spear tail relief valve" is located and not how it works.

My stop ring "freeing" tube is 12 mm OD, 10 mm ID and 3 cm long; I keep it inside my left dive glove. If I ever drop it then I can soon make another one. My dive knife has a hammer on the butt, being more heavy duty than my "finishing knife" which just has a soft rubber handle.

The diameter of the shank or groove on my brass spear tail is 5 mm, so the "O" ring is loose in the groove, it can flop around slightly on the spear tail.

 

[popgun pete]

I have now used a better set of metal vernier calipers (the others were plastic) and the shank on the loose or tilting "O" ring spear tail valve arrangement actually has an OD of 5.5 mm, whereas the shank with the drilled vent hole arrangement has an OD of 6.0 mm. This earlier back and forth sliding to open and close "O" ring spear tail valve is a year 2000 version made from stainless steel and is very short in length, the stop shoulder being right next to the "O" ring groove rather than much further forwards as it is on the brass versions. In the "Black Sea" gun the spear tail valve is only there to allow you to pull the spear out of the charged up gun if you want to render it safe without shooting, or to pump the inner barrel when pre-flooding the gun to purge any air bubbles out of the hydraulic system (which is a necessity for the gun to work properly). In the standard "Aquatech" and later "Dnepr" guns the spear tail valve lets you charge the gun up with multiple spear insertion strokes, or a series of very short spear strokes keeping the spear well down within the inner barrel, so you don't need a long arm reach to charge these guns up for shooting, which is unique to this type of system.

 

[Jegwan]

I have now used a better set of metal vernier calipers (the others were plastic) and the shank on the loose or tilting "O" ring spear tail valve arrangement actually has an OD of 5.5 mm, whereas the shank with the drilled vent hole arrangement has an OD of 6.0 mm. This earlier back and forth sliding to open and close "O" ring spear tail valve is a year 2000 version made from stainless steel and is very short in length, the stop shoulder being right next to the "O" ring groove rather than much further forwards as it is on the brass versions. In the "Black Sea" gun the spear tail valve is only there to allow you to pull the spear out of the charged up gun if you want to render it safe without shooting, or to pump the inner barrel when pre-flooding the gun to purge any air bubbles out of the hydraulic system (which is a necessity for the gun to work properly). In the standard "Aquatech" and later "Dnepr" guns the spear tail valve lets you charge the gun up with multiple spear insertion strokes, or a series of very short spear strokes keeping the spear well down within the inner barrel, so you don't need a long arm reach to charge these guns up for shooting, which is unique to this type of system.

Thanks for your answer and info. Both of the pictured types of spear tail valves in brass has shank OD 5.8mm.

Yes, you are right. The spear tail piston with the "sliding" "O" ring and the drilled vent hole arrangement is the one that's mentioned in the operation manual making it possible to pump the inner barrel with water or to charge the Dnepr. That was why I was surprised with the one with the fixed "O" ring I got together with the Black Sea gun. The one with the fixed "O" ring made the spear come out of the gun when I pumped the hydro pump when the trigger piston did not seal. The spear with the sliding "O" ring stayed at it's position, but water past trough the drilled vent hole and came out of the end of the barrel. It is possible to take the spear out when the gun is charged with both types of spear tail pistons, but the spear tail piston with the fixed "O" ring makes quite a vacuum when doing so. I suppose that using the spear tail piston with the sliding "O" ring will mean that water will leak into the barrel trough the drilled vent hole when shooting the gun.