2 Mini Pneumatics from the 80's

[Stamatis]

I tested the little thing twice. I never caught anything. The ring that restrains the shaft broke partially (I don't know how to call it). Aiming is really poor. But the worst thing is I couldn't catch a dead fish with it if I tried. It was really slow, the fish evaded the shot everytime. I even poked a sitting mullet! I am thinking I should replace the shaft for a 7mm with one "wing" (I don't know how to call that either).
Maybe give it a vaccum muzzle?

 

[popgun pete]

Just pump it up to the maximum pressure, those small guns are only useful when fully charged. The gun being so short you will have no trouble loading it

 

[Stamatis]

Just pump it up to the maximum pressure, those small guns are only useful when fully charged. The gun being so short you will have no trouble loading it

I think I did from the beginning. I predicted that. I can't tell exactly though 'cause I don't have a gauge.

 

[popgun pete]

maximum pressure is whren you cannot force the pump handle down as the pressure is toonhigh. At maximum pressuregaps open up where the tank meets th

I think I did from the beginning. I predicted that. I can't tell exactly though 'cause I don't have a gauge.

Maximum pressure is when you cannot force the pump handle down as the pressure is too high. At maximum pressure gaps open up where the tank meets the plastic end sections, i.e. the rear grip and the nose cone. Don't worry, you will not blow the gun up as the pump will only delivery 40 atm at most and the pump barrel will get hot from adiabatic heating by then.

 

[Stamatis]

maximum pressure is whren you cannot force the pump handle down as the pressure is toonhigh. At maximum pressuregaps open up where the tank meets th

Maximum pressure is when you cannot force the pump handle down as the pressure is too high. At maximum pressure gaps open up where the tank meets the plastic end sections, i.e. the rear grip and the nose cone. Don't worry, you will not blow the gun up as the pump will only delivery 40 atm at most and the pump barrel will get hot from adiabatic heating by then.

Oh, you mean that much! Ok I'll see what I can do!

 

[Stamatis]

This little thing still itches my brain! I tried to pump it to the max, but I can't seem to accomplish that by using only the pump. I still tried a few shots, yet it was still very week. Couldn't even get a sitting mullet.
I am thinking about trying a 7mm shaft (it has an 8mm).
A dry barrel kit is an overkill, huh?

 

[popgun pete]

There must be something wrong with your hand pump or the pump connection leaking air as I used to pump my “Miniministen” up to the max (never checked the actual pressure, but no more air could be stuffed into the gun) and then I really had to lean on the loader to cock it. The spear jerked out of the gun and flew to the end of the line wraps, although it had begun to fall as the short shaft just lacks momentum. You don't need a dry barrel kit or a 7 mm diamer spear, but you do need momentum and thus hitting power to skewer your target.

 

[Stamatis]

Well, all that I described took place during August, but I am pretty sure I did about 60 pumps, and according to the manual, 30 pumps deliver 20atm. Looking at the manual again, it seems odd that the 40cm version needs 105 pumps for 20 atm. Furthermore, the 50cm needs 205, the 65cm needs 255. It doesn't make sense. There could be something wrong with the table.

 

[popgun pete]

More likely the pump connection as if it leaks air then you never get the full pump stroke into the gun and as the pressure gets higher you lose more air on each stroke. Think of it this way, the stroke of the pump represents a certain volume of air and if say the volume of the gun interior is 20 times the volume of the pump then as the gun already has one atmosphere of pressure in it at the start a series of 20 pump strokes will add another atmosphere into the gun bringing it up to 2 atmospheres. Another 20 pump strokes will transfer another atmosphere of pressure and the gun will now be up to 3 atmospheres. Now in reality the pump connection has a dead space and when you pull the pump handle back for the next stroke the compressed air in the dead space is lost, so the ultimate pumping limit is set by the dead space and it never can be zero volume.

Which manual are you referring to as you have two guns, a GSD and an ASSO.

 

[Stamatis]

More likely the pump connection as if it leaks air then you never get the full pump stroke into the gun and as the pressure gets higher you lose more air on each stroke. Think of it this way, the stroke of the pump represents a certain volume of air and if say the volume of the gun interior is 20 times the volume of the pump then as the gun already has one atmosphere of pressure in it at the start a series of 20 pump strokes will add another atmosphere into the gun bringing it up to 2 atmospheres. Another 20 pump strokes will transfer another atmosphere of pressure and the gun will now be up to 3 atmospheres. Now in reality the pump connection has a dead space and when you pull the pump handle back for the next stroke the compressed air in the dead space is lost, so the ultimate pumping limit is set by the dead space and it never can be zero volume.

Which manual are you referring to as you have two guns, a GSD and an ASSO.

I am talking about the Asso.

 

[popgun pete]

Here is the "Asso" pump table.

We can work out roughly the interior volumes of the various models. The 30 cm model requires 12 pump strokes to reach 10 bar, so to double that pressure to 20 bar should take 24 pump strokes. The table indicates 30 pump strokes because of the loss of air during pumping caused by the dead space in the pump to gun connection. That loss is more pronounced at higher pressures because the dead space volume then contains more gas at the higher pressures. Using the lowest figures as a guide the table tells us that the interior volume of the 30 cm "Asso" gun is relatively small if it only takes 12 hand pump swept volumes to raise the pressure in the gun from 1 atmosphere to 11 atmospheres absolute (10 atmospheres gauge). Hence the 30 cm gun interior volume must be 12 times the hand pump swept volume divided by 10 as if we reduce the volume by a factor of 10 then the internal pressure must go up 10 times.