Scubapro Magnum 45 speargun pistol help

When I went out to prepare to go spearfishing a couple weeks ago I realized that my Riedel speargun had been stolen. I knew my fishing poles were gone but was a bit heart broken when I remembered that my speargun was leaning in the same corner of my garage as my missing poles were.

Anyway, I canceled that trip for lack of speargun. Later I remembered that I've got a Scubapro Magnum 45 speargun pistol. It's pneumatic and has a place in the back where it pumps up. What I need to know is how many times should I pump it up and does it need to be pumped every time or can I get a few shots from one session of pumping? Is there a maximum number of pumps that is safe?

Thanks in advance

If the gun does not leak you don't need to pump it at all. It's a closed pneumatic circuit. When you load the shaft it compresses the air, when you pull the trigger the pressure propels the shaft.
Best is to take it to a shop and have it checked.
You can check it yourself but be VERY CAREFUL when loading/unloading the gun in and out of the water, you don't want that rusty shaft in your skull 
First test to gun to see if it has any pressure.
Brace the gun on your knee and point it AWAY from you (and other bystanders). Place the shaft in the muzzle and slowly push the shaft into the barrel (load it) for a few inches. If you feel resistance then it has pressure. DO NOT load it all the way ...because then you have to pull the trigger to unload it!
The pressure should be around 25-30 psi (but I'm not sure). The number of pumps to get to that pressure is dependent on the size of the gun.
If it loads too easy then you don't have enough pressure. Pump in 25 pump increments then try again the loading resistance, when it's right it should feel like as if you would pull on your polespear rubber...or something like it...grrrrrrrrrr

If you overpressurize it you can blow some seals or even destroy the gun.
Never fire a pneumatic out of the water.
Be VERY CAREFUL when loading and unloading.

man, you are a brave soul to use a pneumatic. when i was working at the dive shop there was a mares in for repairs, owner brought it in with shaftin the gun saying he could not get the shaft out or the gun to fire. i was walking it to the back and the gun went off luckily i was carrying it pointed down.

the mares rep told me the gun should be stored standing up for some reason. maybe to do with keeping seals good?

john