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Help Out Everyone - At Which Pressures Do You Run Your guns?

Diving Gecko

shooter & shooter
Jun 24, 2008
1,209
293
138
Shanghai
Hello Gents (and Ladies),
I am quite interested in what pressures and loading forces shooters of pneumatics can load their guns.
I thought about adding a poll, but it may be confusing as there are different pistons sizes out there.

So, I would be super happy if you would take a minute to post:
A). What pressure is your gun(s) at?
B). Which piston size does? (If you don't know, just put in your model of gun and approximate age of your gun and we will figure it out together)
C). What determines your pressure? (Do you pressurize the gun to the max that you can load?)

If you don't have a pressure gauge, you can use a bathroom scale. Just tell us what the scale reads and we will do the math and come up with an approximate pressure. Put the gun on the scale and load the spear about 10-20cm into the muzzle while observing the scale read-out. No need to latch the gun fully! And please be careful!

Thanks so much!
 
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Diving Gecko

Diving Gecko

shooter & shooter
Jun 24, 2008
1,209
293
138
Shanghai
I'll start with some of my guns.

One Air 120
Pressure: 29bar
Piston: 11mm
It is just about the most I can load, but not wearing me out completely. It is a long gun for a pneumatic and I use a double loader, the use of this and the length of the gun works well for me and I feel I can easily and efficiently put force into the loading.

Seac Hunter 90
Pressure: 18-19bar
Piston: 13mm
This is about the most I can load on this gun and it is a bit low. The spear is 6.75mm and quite wobbly. Maybe the length of the gun has something to say in terms of how I can exert "bodily force" on it during loading.

Mirage 80
Pressure: 33bar
Piston: 13mm/10mm
The Mirage can be loaded at higher pressures than my other guns as you load it in a smaller bore barrel (10mm vs 13mm). I could probably load this gun at higher pressures given how I can load my 11mm gun.
 
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Diving Gecko

Diving Gecko

shooter & shooter
Jun 24, 2008
1,209
293
138
Shanghai
I recently serviced a Predathor for fellow spearo and he ran it a 25 bar. I didn't check the pressure before taking it apart, but that's what his meter reads, he says. This is higher than I can load 13mm guns at but he's a big guy and he only shoots it with an 8mm spear.

Julian's Predathor 100
Pressure: 25bar
Piston: 13mm
Spear is 8mm which likely helps in loading higher pressure
 

Nico66

Member
Jun 6, 2017
36
18
23
31
Fr
Hi David,

Here are my set up:

Mares sten 84cm /19,5 atm/13mm piston/power regulator/ 7mm*95cm shaft/salvimar vaccum kit

Mares sten 100/ 20,5atm/13mm piston/power regulator/7mm*105cm shaft/ salvimar vaccum kit.

Hybrid mares sten-seac asso 115cm /22atm/13mm piston/7mm*125cm shaft/ pelengas kit

And my new speargun i ve only tested once (but it already works pretty well):
Hybrid mares sten-seac asso 135cm / 20 atm (i will test 21atm next time)/ 13mm piston/7mm*145cm shaft/ pelengas kit.

In fact, i think that for each gun you have to find the pressure it allows to have the best ratio power/accuracy (and you can load). The improvements (adding vaccum kit/ pulling out power regulator/improving airflows), are juste usefull in order to lower the pressure (and actually make the loading easier). In All the cases my shaft is stopped by the end of nylon (and a little of the dynnema reel is pulled out)
 

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popgun pete

Well-Known Member
Jul 30, 2008
2,630
484
123
Australia
I recently bought some pressure gauges, but ultimately it is what I can load against as the gauge tells me that the pump connection has not leaked and I still bleed air out until I can load it, just. Main problem is a gun that you have not used for some time can suffer from piston stick and to budge it without bending the spear it is best to let some air out. Once the piston is moving again then I put the air back in and once more I check if I can just load it and I don’t bother checking the pressure. Each time you measure the pressure you let some air out, the larger the gun the less effect it has. When checking pressure the gun should be set to full power if it has a partitioned reservoir power regulator, throttle power type regulators don't lock up air so you can forget about them.

The main criteria for loading is can you load it for half a dozen times without turning yourself inside out and the spear goes in without bending excessively, bearing in mind on long shafts they always bend a little as the spear starts moving, that being the longest unsupported length until the gun swallows more of the spear.

A pressure gauge is a handy way to check your gun for very slow leaks as you can leave it screwed in for weeks and see if your gun has a slow leak, but make sure first that the gauge connection is not causing the leak by sticking the back end of the gun with gauge in a bucket of water with a drop of detergent in it. Any froth forming on the surface of the water and you have a connection leak.
 
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Crispin

Spearfisherman ;=- --->
Sep 14, 2001
259
30
118
Auckland
www.blocksoft.co.uk
One Air 100
Pressure: 25-30bar
Piston: 11mm
100 length is just about manageable on these pressures with the 11mm barrel

Cressi SL 100 Tovarich
Pressure: 20bar
Piston: 13mm
I just cant load this any higher - the 13mm barrel makes it really hard - thats why im cutting it down to 85.

Cressi SL 70 Tovarich
Pressure: 30bar
Piston: 13mm
I can comfortably hold this in a position where I can exert a lot of loading force onto it, for it's length it's the most impressive gun i've ever used - utter cannon.
 
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Diving Gecko

Diving Gecko

shooter & shooter
Jun 24, 2008
1,209
293
138
Shanghai
One Air 100
Pressure: 25-30bar
Piston: 11mm
100 length is just about manageable on these pressures with the 11mm barrel

Cressi SL 100 Tovarich
Pressure: 20bar
Piston: 13mm
I just cant load this any higher - the 13mm barrel makes it really hard - thats why im cutting it down to 85.

Cressi SL 70 Tovarich
Pressure: 30bar
Piston: 13mm
I can comfortably hold this in a position where I can exert a lot of loading force onto it, for it's length it's the most impressive gun i've ever used - utter cannon.
Wow, that Cressi 70 at 30 bar is nuts. 10 bar higher than the same gun in the 100 model. But I guess it shows that the length of the gun, and possibly the shaft, decide what position your body will be in during loading - and hence how much force you can put into it.
So, you want to cut the 100 down to an 85 as it will "fit your body" better for loading?
 
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Diving Gecko

Diving Gecko

shooter & shooter
Jun 24, 2008
1,209
293
138
Shanghai
Hi David,

Here are my set up:

Mares sten 84cm /19,5 atm/13mm piston/power regulator/ 7mm*95cm shaft/salvimar vaccum kit

Mares sten 100/ 20,5atm/13mm piston/power regulator/7mm*105cm shaft/ salvimar vaccum kit.

Hybrid mares sten-seac asso 115cm /22atm/13mm piston/7mm*125cm shaft/ pelengas kit

And my new speargun i ve only tested once (but it already works pretty well):
Hybrid mares sten-seac asso 135cm / 20 atm (i will test 21atm next time)/ 13mm piston/7mm*145cm shaft/ pelengas kit.

In fact, i think that for each gun you have to find the pressure it allows to have the best ratio power/accuracy (and you can load). The improvements (adding vaccum kit/ pulling out power regulator/improving airflows), are juste usefull in order to lower the pressure (and actually make the loading easier). In All the cases my shaft is stopped by the end of nylon (and a little of the dynnema reel is pulled out)
Hey Nico.
Your pressures seems to be close to mine at 19-22bar for 13mm guns.
Also, I agree that more testing would be beneficial. I would love, one day, to have proper access to a pool and tune each gun "Majd" style.
E.g. on my last trip with the long Mirage I felt that 7.5mm shafts were somehow nicer than the 8mm ones - but without proper accuracy and penetration testing it's hard to know for sure what's going on.
I always wondered if airgun shafts can whip at higher pressures. They are only supported at the very ends and with the sudden power going into them when fired, they might actually buckle and start whipping... We need some slow mo video of high powered long pneumatics at some point;-)
 

popgun pete

Well-Known Member
Jul 30, 2008
2,630
484
123
Australia
30 bar seems to be the quoted limit these days for most manufacturer’s guns from Italy, although the hand pump can be squeezed to push them up to 40 bar. Guns are built with a certain factor of safety, running at higher pressures uses some of that safety margin up, plus muzzle loading is very difficult. Body positioning certainly plays a factor as well as the shape of the instep on your fins. I use Farallon Farafin II open heel spring strap fins with Moray hard sole dive boots and this creates a stable handle position for loading off the foot.

As for shaft whip that occurs as the spear starts forwards, but a pneumatic gun shaft is supported by the muzzle centralizing washer, so only the emerging shaft can whip and as it is too short to whip then there is no effect. Meanwhile the unsupported length inside the inner barrel shortens rapidly and the shaft emerges from the muzzle without any whip.

A long thin shaft may whip inside the inner barrel, say 6.5 mm diameter and over a meter in length, but again the centralizing washer serves to iron out the bends. The key difference with pneumatic and hydropneumatic guns is the spears are axial tail driven, whereas in band guns they are driven slightly off-axis. That means the resistance at the tip is axial, but the drive is slightly above the spear axis, so a small couple is applied to the shaft, especially with tabbed shafts.

Some band guns had long close fittings muzzles, such as the old "Ocean Rhino" Professional muzzle, which served to iron out the shaft as it passed through the long guide. The drawback is increased friction in the muzzle as the shafts rubs on it on the way through, also clearance has to be provided for the ears on the shaft that collect the line slide and stop ring on the way out of the gun muzzle. The spear has an anti-rolling slot in the tail, hence the shaft leaves the sear box with the ears in the horizontal plane that coincides with the axis of the shaft and allows them to pass unhindered by the muzzle.
 
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