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A042 - Titanium Spearfishing Spear Gun Lantan Underwater Dive Speargun

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

Well-Known Member
Jul 30, 2008
I was looking at Alibaba for some cheap sports watches when on a whim I had a look at "spearguns" and to my surprise this came up.

Now I remember reading about this gun under a different designation in "Underwater Sportsman" some years ago, but did not know if it ever went into production, yet here it is! From memory it is a hydropneumatic speargun and it has interchangeable barrels, much like the earlier RPS-3. Now bar a special edition run of an updated RPS-3 sold as the "Wasp", the extra longer barrel versions of that gun never appeared. Yet here this AO42 gun is, which until I saw it on Alibaba just now, I never knew that it was available.
AO42 Speargun sizes.jpg

AO42 Speargun.jpg

AO42 Specs.jpg
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From the good: 1. Downloading the receiver with air is original! 2. The possibility of lengthening the receiver! 3. Interesting design! From the bad: 1. The use of titanium for the receiver will eat the piston orangi at the point of contact with it! After prolonged storage under pressure, the O-ring rubber of the piston will stick into the titanium and with the first movement of the piston some of the rubber will remain on the receiver! Titanium trunks in pneumatics were abandoned 30 years ago precisely because of the rapid wear of the piston O-rings! 2. A valve with a piston seal, as was correctly said, must be done either segmented or with a hole on the bronze shank overlapped by a 0-ring, but not with a cuff!
3. The coil, if done on a muzzle, it can only be used for winding a harpoon line as an auxiliary for the main coil near the handle on the receiver! Otherwise, the trophy jerking under the hunter breaks the gun out of the hunter's hand using the length of the gun as a lever! Muzzle cone is quite suitable for winding a harpoon line as an inertialess coil
These are the drawings and photographs of the gun’s various prototypes from the magazine.
hydropneumatic gun rear handle schematic.jpg

hydropneumatic gun rear handle.jpg

Unlike the RPS-3 it uses an annular piston as the moving bulkhead to separate compressed air and water inside the gun. In some respects it is similar to the Aquatech guns which use the same moving bulkhead, but here the trigger is mechanical rather than a hydraulic valve operation as is used in the Aquatech. The gun still has a releasing valve, but it cannot move rearwards until the trigger is pulled, whereas in the Aquatech there is a hydraulic locking chamber that only lets the releasing valve move rearwards by dropping the pressure in the locking chamber through opening a pilot valve with the trigger.

An interesting aspect of this gun is the safety in front of the trigger also works as a power regulator that limits the releasing valve opening fully and throttles the shot if you put it in the low power position. In the full power position the releasing valve fully opens to unplug the inner barrel. The rearward movement of the releasing valve is facilitated by the line release finger on the top of the handle being unblocked when the trigger is pulled, and that allows the line release finger to be pulled forward by the departing shooting line. Hence this gun uses the lower tip of the line release lever/finger as part of the trigger mechanism.
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This is how the safety works by rotating the control lever to one of three positions thus making the gun safe, placing it on reduced power or on full power.
hydropneumatic gun rear handle trigger opn.jpg
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Thanks, I was trying to find the website, but searching had found nothing. It says in the specifications that it has a stainless steel inner barrel which makes me wonder what Zahar is talking about when he speaks of piston seals sticking and wearing out.

A stainless steel cylinder is a barrel in which a harpoon with a seal walks! The piston goes one part on the barrel stainless and the other part on the receiver of titanium!
A stainless steel cylinder is a barrel in which a harpoon with a seal walks! The piston goes one part on the barrel stainless and the other part on the receiver of titanium!
I still don't understand, I have three titanium guns, the Aquatech "Black Sea" has a stainless steel inner barrel tube, titanium receiver (tank tube) and a stainless steel releasing valve and works in a similar fashion to this gun. The only thing that may be different is that when the gun is stored I can remove the releasing valve.
Aquatech caps 1.JPG

White plastic caps are temporary covers over screw threaded rear ends to keep dust and dirt out.
P.S. On reflection all the end bulkheads are stainless steel in my "Black Sea" titanium gun, so the stainless steel releasing valve does not bridge two different metals, hence there is no galvanic pair. If this "Titan" AO42 gun has the same arrangement then they would have no problem, unless the rear bulkhead is made from titanium, it being a part that is screwed into the rear of the tank tube.
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From the handbook.
gun assembly variations.jpg

schematic from handbook.jpg

and now translated.
gun assembly variations.jpg

schematic from handbook English.jpg

Note the front bulkhead is also a reel body for extra line storage in addition to line wraps on front and rear line hooks on the top of the receiver or tank.

The full "combination" set costs 700 dollars AUD, plus shipping. The "middle" version costs 500 dollars AUD, plus shipping.
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For comparison purposes this is the Aquatech hydropneumatic gun that uses a hydraulic trigger valve to release the main valve that plugs the inner barrel.
Aquatech layout.jpg
A stainless steel cylinder is a barrel in which a harpoon with a seal walks! The piston goes one part on the barrel stainless and the other part on the receiver of titanium!
This is what you are talking about?
detail notes.jpg
In the Aquatech guns if you pull the spear forwards after cocking the gun then you can push it back again with another barrel volume of water to add to that already injected into the gun. This happens as loading pressure from your pushing effort sends the releasing valve rearwards, the releasing valve moving by allowing water to flow forward through the tiny transfer port drilled into it, after which it returns to the barrel plugged condition courtesy of the big biasing coil spring and water flowing back through the transfer port. The port is very small so that next to nothing can move through it during actual shooting of the gun, but when loading everything is moving much slower and water in small amounts can transfer back and forth.

Now in this GIRS-"Titan" gun the releasing valve cannot move, therefore multiple loading strokes must blow water past that cuff on the piston nose to add more water into the gun, or it has a radial drilling and a ring or rubber sleeve valve to let water in, but right now I don’t see such a feature in the latest drawing.
hydropneumatic gun schematic english.jpg
(original drawing shown)
The gun certainly can be multiple spear stroke loaded as it is stated in the specifications.

Like nearly all hydropneumatic spearguns it will be a sinker after the shot, which limits its appeal in saltwater/off-shore usage as drop it and you may lose it to the depths. However you can always connect a lanyard to the butt if you can easily overpower your prey.
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Well hopefully I will soon find out as I ordered one. I already have the rear handle which is black plastic and contains the trigger and line release lever with the revolving cam that acts as both a power regulator and safety.
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Note that if you want to translate the operating manual referenced earlier then you download the pdf file to your computer and use Google Translate to read that file which will result in an English translation. What it will not do is include the figures or the format of the tables, the latter only being shown as a string of text which can easily be put back into a table format after pasting the whole lot into a Word document.
An interesting aspect of this GIRS-TITAN gun is how you pump the gun to create the pressurised air in the tank. Like all the annular piston hydropneumatic guns the compressed air tank is in the nose end of the gun which means a rear pumping attachment will not work. Usually the hand pump straps onto the nose of the gun with a tank clamping arrangement and stands perpendicular to the gun's longitudinal axis. However this gun is rather different as you unscrew the muzzle and replace it with a plug which uses the same muzzle attachment thread and then insert a spear tail first into the rear of the gun’s inner barrel after unscrewing the rear handle and pulling out the releasing valve. The spear is pushed into the inner barrel a short distance and then trapped in the gun by using a bush fitting which replaces the rear handle and converts the entire gun body into a pump. The tubular hand loader now becomes the pump handle by screwing it onto the threaded end of the spear which normally carries the spear tip but is now facing rearwards. The spear is now a pump rod (it has a tail seal which now serves as the pump piston). You pressurise the gun in the usual way with multiple pump strokes after which those extra parts are removed from the gun and the muzzle, releasing valve and rear pistol grip handle are reinstated ready for spearfishing. To let pressurised air out there is an air release screw (part 17) under the muzzle end of the gun that radially penetrates the front pressure bulkhead. This bulkhead is set back from the muzzle and the outer nose cone that can function as a line spool.
girs-titan gun pump mode R.jpg

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