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[Troubleshooting]Pneumatic Gun (SEAC asso 90) don't shoot anymore

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Sep 6, 2020

Since a few days, my gun seems to have issues shooting.

When I pull the trigger, it feels normal (not hard, no weird noise etc..), the tank pressure is good, but absolutely nothing happens, it's like i don't press the trigger at all.

- First, it did it once during a dive, I couldn't shoot for like 20 minutes and after pressing the trigger about 300 times it worked again.
- Now, it seems to not want to shoot at all anymore: to get the spear out during my experiments, I needed to "sit" with my fins on top of the shaft barbs open and push like crazy while pulling the trigger.
Not the best way to catch a fish and probably not the safest neither, but I couldn't get back home with a loaded gun.

No problem reloading the gun afterwards, this works perfectly too (just the same hassle to get it to shoot again!).

Does anyone have an idea of what might the issue might be?

Thanks in advance!
In your trigger mechanism you have a spring-loaded pin (I believe) that when the trigger is pushed, goes inside the barrel (this pin has an o-ring since it is activated from the outside when you push the trigger), and releases the "hook" that in a loaded position latches onto the end of your piston. So when you push the trigger, via that pin, the hook goes up, the piston gets released and pushes out the spear under air pressure. You need to get schematics for your gun and get your hands dirty I believe - that is what I did. The issue is with that pin - a spring is screwed or something else - you for whatever reason do not release the hook. Start digging
Rather than guess it is better to take the gun apart and see if something has come adrift. The Asso parts diagram is attached. If you depressurize the gun, unscrew the muzzle and use the spear to pull the piston out then you can see if the piston tail is bent. You can also check the trigger operation with no fear of being shot. Disassembly instructions are available here. https://forums.deeperblue.com/threads/pneumatic-dismantling-how-to-get-inside.90024/

Seac Sub Asso original.jpg
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If you are going to open the gun up then stand it nose down in a comer to send all the oil to the front end of the gun. That way when you release the air pressure you avoid blasting oil out of the gun. You always get some oil mist, but leaving the gun nose down for about an hour gives the oil time to flow down to the nose cone end of the gun.
Thanks to both of you for your answers!

I will dismantle it and have a look to the piston and trigger mechanism.

About putting the gun nose down, I always store it like that. Is it maybe bad practice?

Thanks to both of you for your answers!

I will dismantle it and have a look to the piston and trigger mechanism.

About putting the gun nose down, I always store it like that. Is it maybe bad practice?

Nose down is the correct way to store it as it keeps oil sitting around the rear piston seal. In the old days Nemrod and Copino pneumatic guns had a rubber cover on the muzzle tip to sit the gun on.
Nemrod Comando pneumatic.JPG
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After investigating, it was too damaged inside, the piston was shattered in piece and as I didn't want to mess things up, I took the gun to the repair guy (there is only one person fixing them on my island - Hopefully my spearfishing buddy new him!).

So he changed the piston and all the O rings and some other internal parts (maybe part of the piston too? I don't know enough about spearguns to tell.)

I haven't tried it yet, let's hope the trigger part was ok and it will work fine.

Thanks again to both of you for your help!
A piston can really only shatter with a shot in the air as the piston speed is much greater with it not pushing a spear through water. Even vacuum barrel guns still push the spear through water although there is no water in the barrel itself. A gun shot in the water after the spear has been pulled out can have a higher piston speed, but whether it is enough to crack the piston I don’t know as I have never tried it. The shock absorber anvil can crack as well and also has to be replaced.

Metal piston and shock absorber guns tend to crack the shock absorber anvil with air shots, I have seen a number of guns like that when fixing them in the past.
Grinta shock absorber crack.jpg
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That's exactly what the repair guy told me, he asked me if I shot out of the water (which of course I didn't do).
In addition to the piston, a few other plastic parts where cracked (including the shock absorber) and/or were completely shattered in multiple small pieces.

Last year, it however happened one or 2 times that I shot, and the spear didn't left the barrel for some unknow reason. As I have a vacum barrel, it couldn't expel the air easily as it doesn't have the holes on the side, so maybe the parts were damaged when that happened, I don't know. (The gun worked fine after, so I wasn't too worried)
Possibly someone else unknown to you fired the gun when not in the water without your permission, the shock absorber being cracked and internal parts shattered into many pieces is what happens with high speed collisions and plastic components. For a spear not to move when you pull the trigger means the gun cannot have released properly as there is nothing in the gun to jam the spear. Even a vacuum barrel gun with a flooded barrel will push the spear out although it will be significantly slowed as water has to exit around the small gap surrounding the shaft. The nozzle type vacuum cuffs are designed to blow open by stretching circumferentially if water is being pushed through them from the rear.
It occurs to me that a piston could be damaged by ramming the spear in so hard that the piston tail hit the top of the sear lever hump that surrounds the sear lever pivot pin which stops the piston moving completely and then split the plastic piston body by driving the tapered spear tail through it as a wedge, but that would take some doing. Plus you would have had to ignore the sound of the gun latching as the sear tooth clicked when it hooked over the piston's mushroom tail. The shock absorber can only crack if it receives an uneven hit or a very strong hit from the piston.
Hi Pete, excuse me for the late reply.

It's not possible someone else than me used it, and thinking about it, may close up shots (piston and spear is stopped the hard way before fully exiting the barrel) cause this type of damage?
I shoot on low power while cave hunting to avoid violent shocks, but maybe I forgot it one day, I don't know! And maybe even on low power it's not that good?
Shooting and the spear running into something like surrounding rocks before fully exiting the muzzle should not damage the piston. It is possible the piston had a flaw in it from new and it eventually broke. A photo of the damaged piston may have provided more clues. That you could push the spear down the barrel to load it and yet it would not be driven out by gun pressure when you pulled the trigger is a mystery as the see-saw or rocker sear lever is very simple in operation. The cracked shock absorber indicates a strong or uneven hit by the piston. Foreign material in the barrel could jam things, but you would feel it and possibly hear it during loading and the repair guy would have noticed it as there would be marks in the damaged piston surface and scores in the inner barrel bore.

Another possibility is someone unknown to you tried your gun out on land, guns and spears need to be stored separately to remove temptation. I remember someone who had a vintage spring gun found the tip of the spear was busted off and it turned out some of his pals had unknown to him shot the spear into a tree. When they wiggled the shaft to try and pull it out the fine tip end snapped off, so they quietly put it back and said nothing.
I found the numbers on the diagram placed for the gun pointing upwards on the page distracting so turned them all through 90 degrees for the more familiar landscape presentation.
Seac Sub Asso original realign.jpg
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