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RPS-5 mid-handle pneumatic speargun from Ukraine (Ружье РПС-5)

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popgun pete

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Jul 30, 2008
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Another speargun from the Arsenal plant in Ukraine was the RPS-5 which was a mid-handle pneumatic. These guns were produced in what was then the USSR and provided local spearfishermen with underwater weapons suited for their hunting environment and types of prey. Hunting was carried out in rivers and lakes and other inland reservoirs that provided a range of freshwater fish, but visibility under gritty conditions with any current running meant shots would mainly be at close range. These waters were not devoid of big fish as there were European Carp and Catfish to skewer, however monsters such as Sturgeon were off limits, probably due to the Caviar industry wishing to preserve fish stocks.
RPS-5 pneumatic spearguns R.jpg

RPS-5 black grip R.jpg

RPS-5 oblique view R.jpg

Note that these guns string their shooting line wraps on top of the gun between a plastic front wrap hook set back from the muzzle and a rear passive line clip also made of plastic. The guns are not as heavy as they look as that big air tank has not much in it and the plastic handles are relatively slim when viewed from end on, however the guns don't float after the shot. Note that there are no muzzle relief ports, so the guns will have hydrobraking during the shot.

When you pull the triggers they slide in the grips, so they operate push rods inside the gun.
 
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These guns are anodized in the familiar green finish seen on all their guns, most of those being variations on monotube forward latching guns where the spear is held in the muzzle by a miniature version of the spring gun trigger mechanism, basically a pull down sear lever. A version of that trigger mechanism is also used in their R series band guns.

After the hydropneumatic RPS--3 with its pegged, transverse sliding, eccentric collar trigger mechanism, which needs to be seen to be believed, the RPS-5 used something a little simpler. Whereas in the West the flattened single piece trigger or Italian rocker was the basis for most pneumatic guns, the USSR used a form of single piece trigger which is a cam that performs the function of both sear tooth and pivot pin incorporated into a solid metal cylinder. This trigger was used in the French Pelletier carbon dioxide guns and is selected because an external lever can roll it while allowing a good torque to be applied from an external trigger, these elements all lying outside the pressure reservoir. Thus it was a surprise to see this system with its operating lever buried inside the air reservoir, something that has rarely been done before or since. The operating lever is in turn pushed by a longitudinal rod that runs forwards through a pressure seal to the sliding trigger mounted in the mid-handle. That is certainly a different way to do it!
RSP-5 Diassemble photos.jpg

Photos from another site, possibly by Hanter, whose fishgun site is no more. The RPS-5 gun shoots a 9 mm diameter shaft very similar to the one used in the RPS-3. The extreme spear tail has a notched lug spread out in a Vee form like a dovetail to jam into the hole in the piston nose. These lugs can break off which means the spear will no longer jam into the piston and will then fall out of the gun. A conic friction spear tall was evidently not considered.
 
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The rear end of the RPS-5 is virtually the same design used for the muzzle on forward latching guns such as the Alpinasub RPP-5EX, the pull rod on that gun replacing the push rod on the RPS-5. This type of eccentric sear lever is also used on the Vlanik pistonless guns.
Alpinasub RPP-5 gun.jpg

sear tooth contact patches.jpg

The lower sketch shows how the eccentric sear tooth works, it requires an annular notch in the spear, in the RPS-5 the annular notch is in the piston tail.
 
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RPS 5 has a significant design flaw in the form of locking screws a, b, c. They cannot withstand the load and the receiver bushing moves the handle towards the muzzle! To avoid this, you have to put a thrust pipe between the handle and the muzzle!
 

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  • RSP-5 Diassemble photos.jpg
    RSP-5 Diassemble photos.jpg
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RPS 5 has a significant design flaw in the form of locking screws a, b, c. They cannot withstand the load and the receiver bushing moves the handle towards the muzzle! To avoid this, you have to put a thrust pipe between the handle and the muzzle!
You can actually see that spreading has happened on the gun with the black plastic handle and dark grey tank tube. This gun had never been sold and was only bought on its own with no accessories. Probably no one got around to fixing it and it just sat in a cupboard at the plant. The gap allows you to see right through the gun and exposes the push rod position. The other grey handle gun has all its accessories and its passport, so it has been used. The split lug on the spear tail broke off on one side at some time and that was the end of that. The two guns were evacuated out of Ukraine not long before Putin's gang arrived.
RPS-5 handle gap R.jpg
 
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The RPS-5 speargun is of 1991 vintage and the serial number on each gun shows the year it was produced with the leading two digits, thus the black grip gun was manufactured in 1992 and the grey pistol grip gun was manufactured in 1993. Bear in mind guns such as the Mares Sten had been around since 1967, so in a sense these guns are relatively recent, spearguns of any type being made in the late thirties.

The mid-handle pneumatic guns that most would be familiar with that are built on a long barrel tube would be the Nemrod guns from Spain. The front pressure bulkhead which is part of the grip handle moulding is actually moulded around the barrel tube so that it cannot move. That means the handgrip and inner barrel are sold as a single unit as spare parts, they don't come apart and that is why there is no sealing ring used where the inner barrel fits into the mid-handle. Earlier guns with metal handles generally have the front barrel screw into the centre handgrip and the rear tank has nothing inside it which means that the rear bulkhead has to screw into the outer tank tube. Screw threads requite thick tank walls and that makes for non-floating guns after the shot.

One metal mid-handle gun that has a full length barrel that runs from muzzle to rear tail cone is the Pirometer or Seabear RP. This very heavy gun has that centre section held in place on the stainless steel barrel tube by a couple of wire circlips burned in epoxy glue and the tiny gap where the barrel pokes through the centre section casting is filled up with a silastic type of material. Anyone who wants to dig the circlips out and free up the inner barrel from the centre section would have to be crazy. That join needs to be pressure tight and completely immobile.
Seabear barrel.jpg
 
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Here is the RPS-5 passport or operating manual, this is the one for the grey handle gun of 1993 vintage.
RPS-5 passport front and rear cover.jpg

RPS-5 passport page 1.jpg

RPS-5 passport page 2 and page 3.jpg
 
And here is the rest of it.
RPS-5 passport page 4 and page 5.jpg

RPS-5 passport page 6 and page 7.jpg

RPS-5 passport page 8 and page 9.jpg

RPS-5 passport page 10 and page 11.jpg


Printed on the softest paper it has amazingly stayed in one piece.
 
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Both of these guns must be depressurized as they arrived with pistons pushed right back. I do have one spear, but it has a busted rear prong, so that will not engage the piston. The rear bulkhead has two holes for engaging a C spanner, but I don't have one that big. I am surprised that they did not put flats on the diameter that the plastic base ring of the rear line clip sits on. The muzzle screws off the black gun by hand as it has never seen water, while the muzzle on the grey version is hand tight, I have not applied any force to it. I do have a hand pump for the grey gun, so will try to put some air into it. I doubt these guns have any oil inside them as although pneumatic spearguns are actually oleo-pneumatic, my experience of rubber seals from this period is that they swell badly on contact with oil. That does not matter with rubber seals used as gaskets in static situations, but it is bad news for dynamic seals as if the rubber swells then they jam. How this was worked around in the distant past was small amounts of grease to lubricate the seal, but not enough grease for the oil from it to be sucked into the rubber body of the seal. In that period seventies through to the nineties rubber seals were of bad quality for civilian goods. For the military, well that was something else entirely. The entire system was paternalistic, you could buy the goods that the State planners decided that you had access to, but of course they listened to what people wanted. What happened next was not so predictable.

For those who don't read Russian the RPS-5 was said to be good for about 3 metres shooting range and was used at 20 kg per cm squared operating pressure, or about 20 bar. Range flying harpoon is stated at 5 metres, but that will be the spear finally flopping to the bottom with no line in tow. Knowing the latter figure makes sense in low visibility as it might stop you from being bagged by a fellow hunter operating in the same location with one of these guns.
 
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I pumped up both guns with the hand pump which is a very stiff unit to operate as you don't get much feel on the pump handle as to whether you are getting anywhere in terms of pressurization. The black handle gun showed no sign of taking on pressure but there was a gratifying click as the piston in the grey handle gun slid down the barrel which I had previously lubricated with a few drops of oil. I had earlier unscrewed both muzzles which budged after a bit of a twist and then retightened them to hand tight. I released all the air from the grey handle gun, unscrewed the muzzle and with a pair of pliers pulled the piston out. As you can see from the photos it is covered in grease which confirms that the guns are grease lubricated. With the muzzle off and standing inverted in a glass jar not a drop of oil emerged from the grey handle gun. The piston carries two rubber seals and is rather short for a pneumatic speargun piston with a stubby tail.
Soviet RPS-5 piston R.jpg
 
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The screw thread on the barrel is of a surprisingly fine pitch and relatively long using the number of thread turns rather than the depth of the thread form to provide the strength that resists blowing the muzzle off the gun.
Soviet RPS-5 muzzle screw thread R.jpg
 
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Ordered a couple of C spanners to remove the rear bulkhead, the sizing is partly determined by the curve that lays on the gun body component after engaging a peg in a locating hole. These diameters don't seem to be indicated on the spanner specs, so I bought the two smaller ones on offer being slightly adjustable. Earlier bought a "40", but that was too big. The bulkhead OD is 40 mm.
SPANNER.jpg
 
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One thing that is missing on these RPS-5 guns is the shooting line anchor at the muzzle. If you look closely at the gun schematic it is intended to be in, or on, the muzzle component, but as we can see the muzzle is simply a plain cylinder with no transverse hole through it. A tight loop could be tied behind the muzzle onto the slim front barrel or I guess something could be tied onto the trigger finger guard, but that might be too flimsy for the job. Depends very much on the prey and whether you can stone it.
 
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I know from working on the RPS-3 hydropneumatic, also made by the Arsenal, that the rubber they used back then is terrible stuff. The RPS-3 is a rubber hose gun that uses pneumatic pressure to squeeze the hose when it is full of water to push the spear out, thus the gun has no oil in it and the air reservoir contains only air. However I put oil on the hand pump washers to make it pump easier which initially it did. After a while I came back to use the pump again and it had seized solid. Only by undoing the pump rod carrier that holds the pump seals with a long blade screwdriver could I drive the pump rod out of the pump body with a hammer. The culprit was the pump seals had expanded with the oil and locked up the pump rod in the pump barrel. Not only had they expanded but when pushed past the pump's breather holes a tiny chunk of rubber was torn out of each washer by each breather hole. So that is why these guns don't use oil. If you can replace the rubber seals with modern rubber rings then they do need oil as grease eventually pushes away from where you need it to be. Omer didn't use oil in the early Airbaletes and they turned to rust buckets inside if any water got in, it does not take much.

Technically pneumatic spearguns are oleo-pneumatic guns and that is how they are described in early patents.
 
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The C spanners finally arrived and it turned out the smaller one is an exact fit, so I opened up the grey handle gun and sure enough not a drop of oil in it. The slight shine on the inlet valve seal is because I put some oil in the hand pump barrel to allow the pump to move more easily, just a few drops, and that got transferred into the gun. As you can see the release mechanism is slightly twisted around on the inner barrel tube, but that would not affect the gun's operation, although it would put a bow in the trigger push rod.

There was a lot of grease on the piston which I have now wiped off to get a better look at it. Seems to be a 12 mm diameter inner barrel, the piston diameter is about 11.5 mm. Note that the mould lines have not worn off the piston seals!
Soviet RPS-5 bulkhead removed R.jpg

Soviet RPS-5 inlet valve R.jpg

Soviet RPS-5 release mechanism R.jpg

Soviet RPS-5 piston clean R.jpg
 
Using the C spanner I removed the rear bulkhead from the black handle gun, it was very tight and did not seem to want to budge at first, so I put the gun out in the sunlight to warm up and that did the trick. Unlike the grey handle gun the mechanism is sitting vertical in the tank tube and on the same plane as the grip handle, whereas with the grey handle gun it has twisted through a couple of degrees. This gun is very clean inside and indicates that it has never been used. Again some oil on the rear faces which was blown in by the hand pump, nothing elsewhere. A bit of loose rubber had sat on the flat valve seat opposite the rubber valve seal so that is why the gun would not pump up. I will pull this gun completely apart as I need to adjust its front bulkhead which has moved and pushed the grip handle forward a couple of millimeters on the barrel tube as discussed earlier. The front bulkhead sits right behind the plastic grip handle.
 
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