People often talk about the difficulty in aiming a pneumatic speargun, but the situation is you look along the top of the barrel or outer tank tube on the rear handle guns to aim them. For the (currently) standard 40 mm OD tank pneumatic gun that means that the spear axis and hence the spear tip is 20 mm below your aiming point when sighting along the top of the gun, that is less than 1 inch of offset. Now as you will be shooting over a distance of several feet you can see that any angular variation in aim is very small to account for this height offset (draw a right angle triangle with height 1 inch and base say of 3 or 4 feet and you will see what I mean, the deviation is about 1 degree). In practice you don't allow for this offset and will simply aim the gun along the sights and note where the shot ends up and you then adjust your aim as experience tells you where the shot will hit the target. This is true for any speargun as their spears do not travel outwards in a dead straight line in any case, there is always some slight deflection from the aiming point, they don't shoot like a laser beam. However the variation will usually not be significant and pneumatics with rear handle layout such as a "Sten" will shoot as accurately, if not more accurately, than a band gun of the same length. Where accuracy does improve is on a longer body gun as the aiming errors (your visual estimate of the sights being "on target" and your required fine adjusting hand/arm/body incremental movements to achieve this state) are more easily corrected as the aiming base line, i.e. the length from front to rear sight (the gun's sight radius), is greater and therefore any deliberate minor muzzle adjustment movement is subtending much smaller (aiming misalignment) angles on that gun. On a band gun you do not truly sight along an axis parallel and coincident with that of the spear, you are always looking slightly above it (due to the hump of the sear box) and on a downward angle through the end of the spear tip, so your sight line is not parallel to the projected shaft flight even if the spear flew dead straight, but the spear does not as gravity pulls the shaft down the further out that it travels on horizontal shots. When sighting along the top of the sear box roof to the top of a muzzle hoop (closed muzzles) then the aiming line will be parallel to the shaft if you sight through the rear of the gun, however you risk getting the back of the gun in your face with a powerful gun with any rear projection like a cocking stock. If in doubt use both hands on the rear grip or one on the butt.
Why the shaft often hits where you aim it is that the spear drops just enough to pass through your aiming point at the shooting distance you are most used to, but you may think that it flew dead straight. By maneuvering yourself to always shoot at a similar distance you "scope in" on your gun. For longer shots you slightly raise your aiming point and accumulated experience tells you by how much and this occurs with any gun provided it shoots straight in a relative sense. Some guns don't (e.g. my Russian RPB-1) because the spear is not parallel to the axis of the gun before its launch from the gun, so the aim will be off as you estimate correct alignment of the spear with the target by the pointing of the barrel or outer tank tube at the target with a pneumatic gun. Such axial misalignment is rare, but can be a problem with forward latching guns such as the RPB-1 where the muzzle alone directs the shaft.
On most pneumatic guns the spear alignment inside the gun is controlled by the piston front face's spear tail socket and the muzzle nose, via a centralizing shaft washer, which are located at either end of the gun and are parallel to the outer tubular body of the gun due to the gun's concentric inner and outer tube construction.
On a pneumatic gun the centre of grip pressure where you hold the gun handle is close to the axis of the shaft because the spear is in the middle of the gun barrel, not sitting on top of the barrel like it is in band gun, hence pneumatic guns do not really need a higher rear grip handle, unlike a band gun if the gun is comparatively light in terms of its recoil resistance (e.g. a typical eurogun). That is why muzzle flip is not a problem on most pneumatic guns. Muzzles tend to lift after the shot due to gun buoyancy once the spear has gone, not recoil (this is for full length tank, floating after spear discharge pneumatic guns, the situation is different with slim forward barrel guns with rear tanks and mid-handles).
I have shot lots of spearguns and the most important thing is that the shot is reproducible each time, you see a familiar "firing solution" coming into alignment and your brain says "pull the trigger now", often without you even thinking about it. This applies to convergent line shooting as well where you estimate where the gun is pointing from a perspective not coincident with the axis of the gun barrel, instead you are looking at where your direct sight line to the fish and the gun's projected spear trajectory will intersect at an angle. This is often referred to as shooting from the hip. Hence you sometimes read the line where a diver says "the gun fired itself" and then there was a hit right where the diver wanted it to be. Change your gun too often, fiddle with the air pressure or the bands in the case of a band gun and you will take longer to achieve the "auto" recognition of a firing solution (at longer ranges) because the gun performance is changing with each power variation. This is why single gun owners who have had years of experience with that one gun are often crack shots and can knock the eye out of a small fish at ranges where you may struggle to even hit it. Plus some luck, but the more you shoot your gun the luckier you will get!
Why the shaft often hits where you aim it is that the spear drops just enough to pass through your aiming point at the shooting distance you are most used to, but you may think that it flew dead straight. By maneuvering yourself to always shoot at a similar distance you "scope in" on your gun. For longer shots you slightly raise your aiming point and accumulated experience tells you by how much and this occurs with any gun provided it shoots straight in a relative sense. Some guns don't (e.g. my Russian RPB-1) because the spear is not parallel to the axis of the gun before its launch from the gun, so the aim will be off as you estimate correct alignment of the spear with the target by the pointing of the barrel or outer tank tube at the target with a pneumatic gun. Such axial misalignment is rare, but can be a problem with forward latching guns such as the RPB-1 where the muzzle alone directs the shaft.
On most pneumatic guns the spear alignment inside the gun is controlled by the piston front face's spear tail socket and the muzzle nose, via a centralizing shaft washer, which are located at either end of the gun and are parallel to the outer tubular body of the gun due to the gun's concentric inner and outer tube construction.
On a pneumatic gun the centre of grip pressure where you hold the gun handle is close to the axis of the shaft because the spear is in the middle of the gun barrel, not sitting on top of the barrel like it is in band gun, hence pneumatic guns do not really need a higher rear grip handle, unlike a band gun if the gun is comparatively light in terms of its recoil resistance (e.g. a typical eurogun). That is why muzzle flip is not a problem on most pneumatic guns. Muzzles tend to lift after the shot due to gun buoyancy once the spear has gone, not recoil (this is for full length tank, floating after spear discharge pneumatic guns, the situation is different with slim forward barrel guns with rear tanks and mid-handles).
I have shot lots of spearguns and the most important thing is that the shot is reproducible each time, you see a familiar "firing solution" coming into alignment and your brain says "pull the trigger now", often without you even thinking about it. This applies to convergent line shooting as well where you estimate where the gun is pointing from a perspective not coincident with the axis of the gun barrel, instead you are looking at where your direct sight line to the fish and the gun's projected spear trajectory will intersect at an angle. This is often referred to as shooting from the hip. Hence you sometimes read the line where a diver says "the gun fired itself" and then there was a hit right where the diver wanted it to be. Change your gun too often, fiddle with the air pressure or the bands in the case of a band gun and you will take longer to achieve the "auto" recognition of a firing solution (at longer ranges) because the gun performance is changing with each power variation. This is why single gun owners who have had years of experience with that one gun are often crack shots and can knock the eye out of a small fish at ranges where you may struggle to even hit it. Plus some luck, but the more you shoot your gun the luckier you will get!
