Band Spearguns

Edited and translated from an original article by spearfishing champion Marco Bardi

The definition of Ballistics in the dictionary is the study of the movements and forces involved in the propulsion of objects. Spearguns seem to follow trends in the market tied to materials, aesthetics and ballistics.  Divers need to discern the real differences among new products in order to avoid a mistake in a purchase. The basis on which he or she makes their choice for a speargun depends upon the preferences of the diver, the places where they dive, and the type of technique they use spearfishing and what type of fish they’re after. It’s necessary to understand the characteristics of the product and to have enough experience to do it before judging its qualities.

The growth in spearfishing and the different techniques divers now use to stalk their prey nowadays has created the need for lighter, more maneuverable, faster and quieter weapons. So let’s look at all the different factors that influence a speargun.

The proper balance of a speargun is much more complicated than one would think. There needs to be a proper balance between the power of the bands, weight of the shaft, the sensitivity of the trigger, ease of swinging the gun, ease of use, and characteristics of actual design combining these elements.

The starting point to judge a band gun is its balance. Many divers make the mistake of unbalancing their guns by adding power to it without even having tried it stock first. Unknowingly, it results in disadvantages instead of the benefits they were after. Overpowering a gun almost always causes a decrease in precision and an uncomfortable shot. Many divers who make these changes do so in the hope of shooting a big fish, but they will loose plenty of chances to land smaller fish as a result of poor accuracy. And this, without having any certainty of running across the big fish they sought.

A capture of a nice fish is very much a reality with a standard weapon without having to resort to a modified Howitzer! Increasing the power of the bands, three negative effects are usually achieved: the first is usually a decrease in the sensitivity of the trigger mechanism, the second is a whiplash effect because of the increased power which acts negatively on the gun jerking it up during the shot, the third is dictated by the lack of balance between the forward pushing force of the bands and the weight of the shaft, the opposing force.

Let’s analyze them better.  The sensitivity of the trigger mechanism is very important. When a trigger mechanism becomes too hard you risk shifting the entire spear gun trying to pull the trigger. If it’s very sensitive you have the advantage of only having to make only a small traction with your finger to release the shaft. With a sensitive trigger the weapon stays pointed firmly at the target whereas with a hard trigger invariably it causes us to shift the gun if even slightly. That minimal movement in the tip of the speargun can change the aim as much as several inches on the final target depending on the distance. In fire arms, especially hand guns, the firing mechanism is fairly sensitive. In spearguns a compromise of a medium sensitive trigger mechanism is okay because the stability of the weapon in the water allows an efficient traction on the trigger for a precise shot. It can’t be too stiff however as it will cause it to lift and shift.  In light guns with a single band sensitive triggers are better whereas in bigger guns with more weight and power a stronger mechanism is fine.   

To sum it up the trigger pull shouldn’t have an effect on the movement of the gun and on light competition style guns where maneuverability is the priority this can be an issue.

The whiplash effect is practically the shift of the gun determined by the quick movement of the bands that push the shaft away from the speargun. This effect is normally only evident on multi-band spearguns. Band guns have various types of barrels and each has its own pluses and minuses. A round small section barrel has the advantage of being easily maneuverable in every direction and is very comfortable and easy to use. This quality lends itself well to medium size guns up to 110cm. This general size is fairly well rounded meeting the principal needs of precision and maneuverability.

Other barrels have more massive shapes that are less maneuverable but more stable during the shooting phase and less influenced by whiplash. These types of barrels are intended for divers who don’t need as much maneuverability and quickness but would rather install more powerful bands to increase range. Obviously it would be useless to have a barrel of greater mass and power if the trigger mechanism became too hard to pull or there were other negative factors. 

In my bigger guns with two bands I prefer the heavier barrels that disperse less energy from recoil and the stronger trigger designs since the priority is range and power in clear water.  On the lighter guns less than a 100cm, which are setup stock for one band, I prefer the feel of the more sensitive hair-trigger and the pin point accuracy for a fast alignment on the target. 

When I change from a standard size gun like a 90cm that’s light and has a very sensitive trigger to a 115cm gun with double bands I always try to remind myself while fishing that the gun has a different feel.

The relationship between bands and shafts is fairly comparable to a javelin thrower and the javelin. Take a strong javelin thrower and give them a javelin that is too thin and during the launch it will vibrate consistently until it falls short because it lost a lot of energy although it had plenty of power behind it. And vice versa, if you take a javelin that’s too heavy for the thrower it will only go a short distance without the power to launch it efficiently. With a lance of the ideal weight for the javelin thrower when it is launched there aren’t vibrations or a loss of energy allowing it to carry its flight efficiently and streamlined.  This is the desired combination we seek with spearguns.

Shafts which are too light with bands that are too powerful waste energy without maintaining the desired direction. Shafts that are too heavy with bands that are too weak don’t maintain a constant direction falling short of the target. Guns with an ideal balance between power bands and shaft result in perfect shots.

There are many types of bands and spear shafts with different strengths and thickness from different producers so it’s not safe to make exact judgments about the relationships between each of them. However 6-6.5mm shafts are a good combination using 16mm bands, and 6.5 - 7mm shafts are a good match for 18mm or 20mm bands. If you decide to use double bands, 6mm shafts should be avoided.

There are lots of speargun designs sharing different concepts generally well accepted and some definitely not accepted. One is the concept of a shaft guide or rail along the barrel. Some firmly believe the shaft guide also known as a rail is necessary for an accurate shot so long as the barrel doesn’t flex (or else it becomes counterproductive). Another way of thinking says a shaft guide or rail has no advantage since the shaft rests between the muzzle and the handle alignment in strait pull screw in bands.

Theoretically if there was any barrel flex under heavy band load, the shaft resting in between two points would have a tendency to shoot more accurately than a gun with a rail, unaffected by the arch in the barrel. The shaft in a rail takes the shape of the barrel if there is any flex. This is more likely to make the shaft bow upwards although its really, in my opinion, only a concern in long 130cm+ guns that may be overpowered. Additionally, the absence of any friction between spear shaft and rail in rail-less guns makes the gun quieter and wastes less energy since the bands are parallel with the shaft.  These last two are almost negligible considerations for most people.  Whatever design is used manufacturers must weigh in all these considerations carefully since there are pros and cons to each. 

Years back it was always thought that inaccuracy was a result of barrel flex and we were always seeking stronger and stiffer barrels. In reality the barrel flex wasn’t the cause of inaccuracy. What wasn’t apparent was that it was more due to the flex between the handle and barrel joints which creates a small angle that magnifies the error considerably during the shooting phase. On long guns this effect is much more noticeable as the long barrels under heavy load flex between the handle and barrel connection. This is a much greater concern to address in development and production than just barrel flex. The latest trends of more solid spearguns specifically address these concerns between handle and barrel joints.  Some handles have a male insert as well as a female receptor that captures the thickness of the barrel thickness in the middle. 



Another point on the subject of accuracy that seems everyone agrees with is the proper alignment between shaft and bands. In other words it is advantageous that the shaft and bands are as parallel to each other as possible.

If the bands pull from below the shaft axis like they do with loop bands it’s likely that the shot will be high as a result of the shaft ramping off the muzzle as the bands pull the back of the shaft tail down. And the other way around, if the bands in the muzzle are higher than the axis of the spear shaft the shot will be low, at the instant the shaft is leaving the muzzle the bands will lift the tail of the shaft pushing the front end down.  Most open muzzle guns have rails or the option of rails to control these tendencies and to ensure the shaft goes out in a strait path regardless of the angle of the bands.

The development of a new speargun must keep all these factors into consideration, the materials used, the reliability of the trigger mechanism, and the balance between the stock shaft and bands equipped on the gun. We should keep in mind that not all spearguns are produced based on these premises and with these prerequisites. Sometimes spearguns are designed for a less technical consumer of which price and simplicity as well as ease of use is more important. More experienced divers will justifiably seek a high tech product, whereas a beginner cannot appreciate the advantages which actually become disadvantages as he or she learns the ropes.

A few other small considerations. One thing to keep in mind is the aerodynamics of a spear shaft and its flight. It could be bent causing it to shoot off target, just as the barb could be too big or not aerodynamic for the shaft, as well as the possibility of the shooting line being too thick, factors that all could possibly lead to a bad shot. Even the type of steel used for the shaft plays an important role. A soft type of steel can be influenced by the power of the push of strong power bands. The pressure will cause the shaft to flex which should straighten it self as soon as it leaves the gun. Soft steel doesn’t have the right memory to return to its original shape fast enough. A more “springy” steel suffers less from this problem during the shot bending less from the traction of the rubbers and springing back to its shape immediately. For these reasons a harder grade spring steel is much preferable to softer grades.  Today’s standard for stainless steel spear shafts is AISI 630 also known as 17-4PH (precipitations hardened) which is steel used for a variety of applications in the spring industry.  It’s high resistance to corrosion is a plus in the saltwater environment.

 
The shooting line. Most commonly a good all around shooting line is 200-300lb test (approx. 100-150Kg’s), between 1.6-2mm which has the combination of great breaking strength as well as fairly low friction in the water following the trail of the shaft. Naturally the smaller the shooting line the less it influences the accuracy during the shot which is why anything over 400lb test on a band gun with a 7mm or thinner shaft is overkill.

The feel of the gun is very important for beginners and seasoned divers alike.  When choosing a speargun many people are comparing features like they do with electronics.  A speargun that doesn’t have a nice feel to it most likely doesn’t fit.  The gun is the extension of our hand in the water and, just like the cat’s paw used to strike the mouse; it has to feel natural and solid.  Comparing different grips and the way they feel and fit in your hand will make it easier to aim and swing the gun around underwater. 

In the general subject line there are lots of other details but there’s a risk of falling into the “maniacal perfection category” since this is just fine tuning and small details. 
Evaluating the right shot is a fundamental quality that only comes with experience.  There are divers that only pull the trigger when they are sure to hit the bulls-eye and others who like to roll the dice and take Hail Mary’s! The former have reached an awareness of the shot that puts them in a position to understand when it’s time to pull the trigger. They practically understand when the fish is at the right distance, when the moment is right so the fish won’t deflect the spear, what the useful range of the gun is…you get the idea.  They hardly ever miss and they’re careful not to take shots that will miss and scare the fish off.  Divers who have yet to really understand how to evaluate the right moment either shoot too early, at the wrong distance, and with enough tension and nervousness built up that scared off the fish before they even shoot.  For them it’s useless to have the most accurate and well balanced high end gun as their priority should be learning on a basic less confusing strait forward setup.  Once they’ve mastered it they can reap the rewards and enjoy the virtues of a more technical gun.

Lastly, understanding the particulars of a speargun and its workings is important but we should never forget that the best thing is going diving as often as possible and there’s no substitute to learn how to shoot a fish. Figuring out one’s personal habits will just help determine what speargun is more ideal.

Marco Bardi / Mark Laboccetta.  Marco Bardi is a three time Italian Spearfishing Champion with several National and International titles under his belt well regarded in for his technical knowledge.  Mark Laboccetta holds 8 IUSA world records and is also a speargun consultant for OMER in Italy and in charge of North America distribution.