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Technisub Conquest Booster Pneumatic Speargun

popgun pete

Well-Known Member
Jul 30, 2008
The Technisub Conquest Booster is a very similar gun to the Mares Sten with a 40 mm tank. It was Technisub's next effort after the Ranger models which seemed to have big tanks but were actually rubberised shrouds that conferred a different shape to the usual grease gun appearance. Under that shroud was a smaller diameter tank and a higher compression ratio which was not what people wanted once they had used the Sten models and the very similar Cressi SL. I expect the same contractor made everyone's guns and the Conquest Booster appeared around the same time as the Mares Competition Line models in charcoal grey and lime green. The First Conquest Booster I saw shared those same colours. In later years the colour scheme changed as with most of the other companies to freshen up the model range.
Technisub Conquest Booster rx.jpg

Technisub Conquest Booster parts diagram.jpg
The Technisub Conquest Booster used a metal piston similar to the one used in the Scubapro Magnum.
Technisub Conquest Booster piston.jpg

This is the one from the Magnum, when Salvimar resurrected that gun as the Vintair it was replaced with a plastic one.
Scubapro Magnum piston.JPG
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Here is the gun before I dismantle it. When purchased it was fully pressurised, but had no spear or pump and was probably a deceased estate as other guns were for sale, but not pneumatic guns. Seems in good shape and was owned by someone who knew what they were doing and did not abuse it, like firing shots on land!
Technisub Conquest Booster RHS R.jpg

Technisub Conquest Booster LHS R.jpg

Given the white grip handle this is probably a much later version as divers dropping a loaded gun often realised too late that guns can "disappear" on weedy bottoms. Spearfishing is then abandoned as the dive becomes search and recovery. Note the safety lever is missing, but the safety cam is still inside the grip handle.
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Finally a hot day and a chance to warm the gun up in the sunlight prior to knocking it apart. The double "O" rings were a strong interference fit and the gun had been put together without grease, only oil. Because I have taken so many guns apart I knew what to expect. The nose cone only came off using my pressure assist method as the "O" rings are hard to budge on the external side if there is no grease there. Oil totally evaporates on the dry side, i.e. the outside has no lubrication. Knowing this I earlier oiled all the section joins to get them to slide easier, but it was a bit of a struggle, took me about half an hour to go from no movement except the muzzle and now it is all apart. Photos later, but the gun is very like a "Sten" inside with a few extra moulded washers that are not really necessary, in fact you will not find them in a "Sten". Quality-wise reminds of the Scubapro "Magnum" where the edict had been, "Spare no expense, we will make it back on what we charge for these guns". Which was a lot!
Here are the photos.
Conquest Booster A.JPG

Conquest Booster B.JPG

Conquest Booster C.JPG

Conquest Booster D.JPG

Note stainless steel shock absorber anvil.
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And some more. Power regulator transfer port plug has a spring to aid the user in opposing gun internal pressure when moving the selector knob to low power which is forward and down in the selector gate. Double "O" rings improve sealing and oppose rear handle twisting out of fore-aft alignment on the gun.
Conquest Booster E.JPG

Conquest Booster F.JPG

The hollow rear grip has the facility to store a small flashlight made to insert inside there, it is held in place by the black lever that locks it in. A bit of a gimmick really unless the gun still floats with the flashlight installed you would be best to stick the flashlight on your belt.

The oil in the gun was very clean, but was trapped inside the pre-chamber, so only really came out when I pushed the guts of the gun out through the back end of the tank, at which moment the oil flowed out onto the workbench. No problem as I have litres of the stuff, so just hosed the workbench down. A good reason to work outdoors, summer is the best time to tear guns down, provided you have weapons to fall back on. As Neo says in the Matrix, "Guns, lots of guns" and you know the rest.
guns lots of guns.jpg
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One quirky aspect carried over from previous Technisub rear handle guns is the long finger on the front of the plastic trigger which swings down and frees the line release built into the top of the trigger finger guard. The bulk of the gun is laid out like the Mares Sten, but it has little extra touches that speak of quality and parts are unique to the gun. I rate this Conquest Booster gun as having much the same build quality as the Scubapro Magnum and is very well made. Pity that Technnisub persevered with their small diameter tank guns and didn't make the switch to 40 mm tanks earlier.
Technisub Conquest Booster line release R.jpg

Note the rather small diameter pivot pins, probably selected to fit the available spaces in the plastic moulding without weakening the cross section of plastic material.
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The non-return valve that provides the easy loading feature can be seen here through the translucent wall of the partitioning bulkhead housing. A coil spring biases the valve and can be seen on the right.
Technisub Conquest Booster non return valve R.jpg
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With nothing further to learn, and no "O" ring kits available that I know of, I reassembled the Conquest Booster without dismantling it any further. The sear lever is the usual see-saw type and the trigger transmission pin is small, but not that small as it is in modern guns. If I pulled the pin out and stuffed its "O" ring then the gun would require repair when it was in perfect condition before I pulled it apart. Basically a Medisten in terms of its dimensions and will use the same amount of oil inside the tank.

Note to take the gun apart any further the trigger is removed and you pull the trigger transmission pin out taking note which end faces inwards. The rear inlet valve body has to be unscrewed using a tool that fits in the notches seen on the body's outer edge. A tube spanner with end lugs that fits the notches will work. Once that is unscrewed the barrel should pull out from the handle, but the power regulator shaft needs to be freed first and for that the front circlip on the partitioning bulkhead needs to be removed or at least slid forwards. Care is needed as these circlips are easy to bust, you need proper circlip pliers. With the circlip out of the way the power regulator body can be slid forwards, but make sure the power regulator shaft doesn't get bent while doing it. Once the sear lever pivot pin is exposed you can knock it out of the inner barrel tube and take the sear lever out. Make sure you don't lose the small basing coil spring that pushes the sear lever tooth up when the gun is not cocked.
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The original colour scheme when first released. From another post on the site.
Technisub Conquest Booster original colour scheme.jpg

Note one easy way to tell if a gun is pressurised is the power regulator position. At operating pressure the regulator control knob is pushed back in the gate, it will only stay forwards if there is insufficient pressure in the gun or the selector is down and snagged on the dogleg at the front of the gate. The odd man out is the reverse gate Salvimar guns which use an upstream rather than a downstream valve like everyone else does in rear handle pneumatic guns. Salvimar guns combine the one-way and power selector valve in one item rather than have two valves.
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