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Pre-season pneumatic gun preparations

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popgun pete

Well-Known Member
Jul 30, 2008
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Hopefully divers will have stored their gun in a clean condition and with the muzzle pointed downwards over the non-diving season to keep the gun's internal oil supply lubricating the rear of the inner barrel sliding piston. However over a long storage period the oil film on the small diameter trigger transmission pin shaft and the power regulator control shaft will have dried out as they are both exposed to ambient conditions even if they are hidden from external view and you cannot directly observe them. To ensure that these parts are moved with lubricant on the "dry side" when the shafts are pushed through their operating seals when you first move them again it is worth pouring a few drops of oil into the power regulator control gate and down around the trigger where the back of it disappears into the grip near the trigger pivot pin. After allowing the oil to penetrate, carefully pull the trigger, it will feel stiff momentarily, then will immediately move freely as the now oiled pin slides in the trigger seal. Do the same with the power regulator, push the cursor knob forwards and down to "low power", then flick it up and the cursor should fly back to the "full power" position (the pressure in the gun blows it back).

Next put the gun into a muzzle up position and pour some oil into the muzzle relief ports and allow it to flow down into the inner barrel, you do not need much oil, so do not overdo it. Insert the spear into the muzzle and load the gun about half way down the inner barrel and then let the spear push back up again while keeping a steadying control with the loading bar while doing this. Don't be tempted to fully load the gun as this can be very dangerous on land! Repeat the exercise and then with the gun horizontal jerk the spear free of the piston to remove it from the gun. Those who have fitted dry barrel kits will have to pour some oil down into the muzzle opening instead, then insert the spear and press down with the loading bar until the piston moves away from the shock absorber face. The oil that you placed in the muzzle opening will run down into the inner barrel and then partial loading can occur as above in order to work the piston seals in the inner barrel once the oil has reached the outward facing seal surfaces. If there are no leaks then you are ready for the coming season of diving, however you might want to add some more air to your gun.

Before doing so crack the inlet valve to let some air out as this will clear the inlet valve of anything that may have lodged inside it by blowing it clear. Put a few drops of oil into the valve opening, connect up your hand pump and perform a few pump strokes into the gun. Stop and check for leaks, if there are any leaks the pump handle will be moved back as air pressure escapes through the inlet valve, then add as much air as you think necessary. Try loading the gun to ensure that you can budge the piston, but don't load the spear all the way, you should know by reaching the half-way point. If at the dive site you cannot load the gun put the power regulator on "low power" and then push in the inlet valve (with a blunt pin, use nothing sharp or you will scratch the inox ball of the inlet valve) and release a short burst of air. Lift the power regulator knob to allow it to move back and re-equalize air throughout the gun's chambers and then move the cursor knob back to "low power" to recommence loading activity. The use of the "low power" setting minimizes the air loss when cracking the inlet valve as the majority of the air is held in the forward air tank, you will be only bleeding down the air in the inner barrel and the pre-chamber behind the power regulator bulkhead. A brief burst of air makes a noticeable difference to loading effort, air comes out much quicker than you would think and you want to avoid dumping air that you may have to put back with the hand pump!

On a Scubapro "Magnum" pneumatic remember that "low power" and "high power" positions are reversed in the selector gate, it makes a difference, I have just been working on one!
 
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These are useful hints for everybody who own pneumatic gun. That might prevent damage to pneumatics.
 
On their "Magnum" pneumatic Scubapro provided two maintenance oiling positions on the handgrip; the round port on the RHS rearwards of the trigger pivot pin lubricates the trigger transmission pin and on the LHS the round port lubricates the power selector rod shaft. If you look very closely at the power selector gate you can see a small plus "+" sign inside the recessed well, that tells you that the forward and down cursor knob position is "full power". Likewise there is a negative "-" sign inside the rear upper section of the well that tells you the rearmost gate position is "low power"; here it is obscured by the cursor. They are not very obvious markings and I never noticed them until I was pulling the gun apart, although I soon figured out that something was different when I tried the gun out before doing so, this one only had a very slow leak. I never received the "Magnum" instruction booklet, so it was a "suck-it-and-see" approach. The oiling points are a nice touch, but you don't really need them, however the LHS image shows you the distance from the selector gate to where the pressure seal is located on the power selector shaft, there is a long connecting tunnel which you need oil to penetrate, however on the "Magnum" the oil can go in immediately behind the seal courtesy of the round port. Scubapro quit making the "Magnum" when they decided to abandon all their spearfishing connections.
 

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Some better photos illustrating the two oiling positions on a Scubapro "Magnum" (and its "re-issue" as the Salvimar "Vintair").
Scubapro Magnum oiling point R.jpg
Scubapro catalogue 1989 R.jpg
 
Although a somewhat photographic style compared with the usual line drawing, Scubapro issued this parts diagram to dealers.
Magnum exploded parts R.jpg
Magnum O rings.jpg

the actual sheet at reduced scale
Scubapro Magnum___1 diagv RR.jpg
 
Just found this photo of a brand new Magnum 45, the smallest version of Scubapro's pneumatic gun that was manufactured for them in Italy and intended to be superior in every respect to the Mares "Sten" series as the same people manufactured them! As a superior construction, thicker and glass reinforced polymer plastic, all alloy parts with no brass and stainless steel used for everything else they were for a period the ne plus ultra of rear handle pneumatic spearguns with prices to match! Very expensive in their day, just like every other item from Scubapro!
scubapro magnum45.jpg
 
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