Pneumatic leaking air question

For you guys knowledgeable about pneumatic spearguns; I have a bran new pneumatic speargun here that when I charge it a little past the manufacturer's recommended maximum pressure, a little air leaks every time I press the trigger. I'm familiar with the parts, the trigger pushes on a pin that travels through a sort of seal, and pushes up on the lever that releases the piston. Why would it only leak when I press the trigger? Have you seen this before? I think this is unacceptable as eventually the gun will lose pressure. My way of pressurizing a pneumatic has been to keep pumping it up until I can barely load it, I've only used a few Mares Cyrano before and this has never been a problem. Could it have something to do with the viscosity of the oil I used? I don't think so but it's worth considering, I use thin oil.

Thanks Harry.

Do you have a source for these pins if it is bent?

Scubasworld doesn't have them. Never mind the pin anyways. I was thinking of the Cyrano pin which is very small. I disassembled the trigger just now and the pin on this gun is much more robust, much more unlikely to bend, and it was straight. I pulled out the valve and O ring, there was plenty of oil in there. But I think I may have found the problem. The O ring is not tight on the pin. I figured that screwing down the valve a little tighter will compress the O ring and make a better seal around the pin. The pin travels through the valve/O ring with more difficulty now. I'll pump it up again and see.

Tightening down the valve and compressing the pin O ring solved the problem.

Core, I don't know how much improvement there's been. To me they look the same as when I started with them a decade ago. They're not that "loud", but the sound is a distinctive "thunk" and carries very far, I'd say 100 meters underwater.

I think any pneumatic shorter than a meter is severely restricted in terms of what kind of fish you can take with with it. More a hole gun than anything else. These small ones you speak of are useless as far as I'm concerned, maybe for taking lobster where spearing lobster is allowed.

There is no maintenance per se. There should be no loss of air or oil. Once in a long while you'll have to disassemble and change the O rings and oil. If they dry rott the gun will leak. It's important if you're hunting on the bottom to make sure that no sand particles get in the muzzle and behind the piston. If you load the gun with sand in there it will score the inner barrel and you'll have an air leak. Then the only remedy for this is to replace the inner barrel. To make sure the muzzle is free of particles, if it came in contact with sand, you can shake it in the water to make sure everything drained out.

One other thing I do if the gun is stored for a long time is alternate hanging it muzzle down then handle down. This will make sure all the O rings come in contact with the oil and will not dry rot.

As far as what else can go wrong, I suppose the piston could break down. Maybe greek knows of more possible failures.