Pneumatic Speargun Pistons

Gazz · Feb 2, 2015

I made this image to show the similarities between pistons (basically very little).
Note: the devoto one was provoted by roman boto for my cressi sub.

In my opinion if your vuoto piston breaks you can use a seac sub one, but you would have to change the Tang on the spear as well.

Diving Gecko · Feb 4, 2015

A lot of them are def interchangable. The Seac (Asso) one has a slightly inferior design by birth as the front of metal part is in contact with saltwater in the barrel. This can lead to corrosion which can spread into and under the 0-ring groove or small specks can fall of and jeopardize the seal or surface smoothness of the barrel.

popgun pete · Feb 4, 2015

Metal pistons worked OK provided that they were made of the right stuff or had a suitable protective coating such as cadmium plating. However you definitely needed to wash the guns out and put some oil down the muzzle and onto the piston nose from time to time. The main question with interchanging pistons is that the mushroom tail fits the sear tooth properly and the sear tooth will hang onto it until you pull the trigger. Another aspect is that the piston nose fits the shape of the shock absorber anvil face so that the impact is not localized and risks cracking the plastic components. Of course you require the piston diameter to match the inner barrel bore, especially now we have 11 mm, 12 mm and 13 mm inner barrels. In the past there were 14 mm inner barrel guns as well.

Iyad · Sep 24, 2015

Hey Guys , Ive got a problem I want to clarify !
Aiming seems to be impossible to me with my SL Cressi 70 cm Speargun !! I never Speared a fish ( rarely) !!
Whats the shooting range ? Is it me ? or that the Gun is not precise !

Gazz · Sep 25, 2015

Iyad said:
Hey Guys , Ive got a problem I want to clarify !
Aiming seems to be impossible to me with my SL Cressi 70 cm Speargun !! I never Speared a fish ( rarely) !!
Whats the shooting range ? Is it me ? or that the Gun is not precise !

Cressi normally has a tight trigger that causes the gun to pull to the left as you shoot (if you are right handled), hence the inaccuracy.
Try holding the gun with 2 hands and or let a little pressure out of the gun for a smoother shot.

Iyad · Sep 25, 2015

Gazz said:
Cressi normally has a tight trigger that causes the gun to pull to the left as you shoot (if you are right handled), hence the inaccuracy.
Try holding the gun with 2 hands and or let a little pressure out of the gun for a smoother shot.

THANKS SO MUCH GAZZ, YOU ARE RIGHT THE TRIGGER IS SO TIGHT ! I will try reducing pressure

Diving Gecko · Sep 25, 2015

Iyad said:
THANKS SO MUCH GAZZ, YOU ARE RIGHT THE TRIGGER IS SO TIGHT ! I will try reducing pressure

Hey Lyad and welcome to DB

The main reason your trigger is hard is that the Cressi gun you have comes with a 3mm trigger pin.
That's the pin which is pushed upon by the plastic trigger and then through a bushing and o-ring goes into the tank to press on the hook (sear lever) which holds the piston.
Most new guns have 1.5mm or 2mm pistons.
If we discount the effect of the o-ring friction and the friction of the hook on the piston, then there is huge difference between 1.5mm and 3mm pins.
If your gun has 20 bar in it, then the force you have to press with to get the 3mm pin moving is 1442 grams while a 1.5mm pin will only need 361 grams.

This is the reason a lot of Italian spearfishermen change the trigger pin on their Cressis because besides the trigger, the gun is solid.

For about 20 euros you can get a custom made 1.5 trigger for your gun. It is well worth it. It's a pretty easy modification to install, too.

Iyad · Sep 25, 2015

Diving Gecko said:
Hey Lyad and welcome to DB

The main reason your trigger is hard is that the Cressi gun you have comes with a 3mm trigger pin.
That's the pin which is pushed upon by the plastic trigger and then through a bushing and o-ring goes into the tank to press on the hook (sear lever) which holds the piston.
Most new guns have 1.5mm or 2mm pistons.
If we discount the effect of the o-ring friction and the friction of the hook on the piston, then there is huge difference between 1.5mm and 3mm pins.
If your gun has 20 bar in it, then the force you have to press with to get the 3mm pin moving is 1442 grams while a 1.5mm pin will only need 361 grams.

This is the reason a lot of Italian spearfishermen change the trigger pin on their Cressis because besides the trigger, the gun is solid.

For about 20 euros you can get a custom made 1.5 trigger for your gun. It is well worth it. It's a pretty easy modification to install, too.

Thanks Diving Gecko for your precious info... In my area spare parts aren't available at all unfortunately!
I will try to reduce the pressure and hold the gun with both hands

Diving Gecko · Sep 25, 2015

I am pretty sure that both Marko (his profile name is "zmajmr") plus the guy I have in mind, can ship worldwide for cheap. I don't know if Marko makes trigger pins mods these days (and if he does, I am not sure of his price), but I can think of one who will very likely make you one and ship it to you. He made two for me already and I paid around 20E/each.

Basically, they are made by guys who love to tinker with pneumatic guns and will make custom spareparts as a small side business - but the truth is, they make much better things than are commercially available.

Let me know if you want their emails and you can check with them. It is a very recommendable modification. I promise, you will like it

The only worry you should have is that you will find out that you can make your Cressi even better with a few other mods, and then you will be hooked, haha.

Iyad · Sep 26, 2015

Diving Gecko said:
I am pretty sure that both Marko (his profile name is "zmajmr") plus the guy I have in mind, can ship worldwide for cheap. I don't know if Marko makes trigger pins mods these days (and if he does, I am not sure of his price), but I can think of one who will very likely make you one and ship it to you. He made two for me already and I paid around 20E/each.

Basically, they are made by guys who love to tinker with pneumatic guns and will make custom spareparts as a small side business - but the truth is, they make much better things than are commercially available.

Let me know if you want their emails and you can check with them. It is a very recommendable modification. I promise, you will like it

The only worry you should have is that you will find out that you can make your Cressi even better with a few other mods, and then you will be hooked, haha.

Ya Please Give me their emails, and I have another suggestion what about changing the spear head to the one that like a fork ! My chances would be 5 times with the regular spearhead !!

Diving Gecko · Sep 26, 2015

Iyad said:
Ya Please Give me their emails, and I have another suggestion what about changing the spear head to the one that like a fork ! My chances would be 5 times with the regular spearhead !!

Hmm, the fork ones are not my expertise, maybe some of the Med hunting guys can chip in. I think it may have it uses but not that many. It slows down the spear a lot, so I think it is mostly intended to stun fish hiding in dens. I have never seen them used for pelagic or more free swimming fish. At least, that's my understanding of them.

Sounds like you need to do some target shooting first and foremost. No matter which gear you have, it pays off to build a small target, take it into shallow water (or a pool), weigh it down and then just start shooting at it until you have more of an idea how your gun shoots.

I'll PM you Marko's and Dima's details and you can email them both and ask if they can make a trigger for you.

Iyad · Sep 26, 2015

Diving Gecko said:
Hmm, the fork ones are not my expertise, maybe some of the Med hunting guys can chip in. I think it may have it uses but not that many. It slows down the spear a lot, so I think it is mostly intended to stun fish hiding in dens. I have never seen them used for pelagic or more free swimming fish. At least, that's my understanding of them.

Sounds like you need to do some target shooting first and foremost. No matter which gear you have, it pays off to build a small target, take it into shallow water (or a pool), weigh it down and then just start shooting at it until you have more of an idea how your gun shoots.

I'll PM you Marko's and Dima's details and you can email them both and ask if they can make a trigger for you.

Thanks so much dude

Diving Gecko · Jul 22, 2016

Just sharing a pic I made today of comparing the pistons I happened to have here:

Pneumatic Speargun Pistons

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Pneumatic Speargun Pistons

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