The first criteria selection of a crossbow will be function of the type of hunting which you practise. If you fish into holes, choose a tube of 75 cm. If you practise only glides or the waiting technique, take one 100 cm. For hunting big fishes, one 110 with reel is essential. Finally I kept the general-purpose one for the end: the 90 with which you will be able to practise (almost) any type of spearfishing... In Mediterranean France, where the visibility, and according to the current regulation, it's very well to choose spearguns provided with arrows "tahitienne" and armed with the only force of sandows.

How to choose his speargun? It is necessary that the handle is ergonomic and that you have a good holding in hand (one will speak about anatomical synthetic rubber stick). The majority of the spearguns sold on the market are provided with one takes down line with fixing under the trigger, which is very practical and prevents the line from being gotten mixed up. Very practical also: the support against the breastbone to facilitate the loading and that one finds on Beuchat Mundial, Sniper of SporaSub or Comanche of Cressi, to quote only these. As for the remainder, it is the type of hunting which one practises and the size of your coin purse which will determine the final choice.

In the Mediterranean sea, one will use the arrow "tahitienne", whose diameter and length will be given according to the type of hunting and the speargun used. Are thus proscribed the three spear points whose thrust force in water is braked (waiting) and from their brittleness (fishing into holes). Their only employment lies in the seas at very reduced visibility (Channel for example) where it is necessary "to rake" wide if one does not want to miss his target. As for the sandows, they are also dependent on the type of crossbow and the practised type of hunting. In general, for the waiting technique and glides, one needs particularly reactive rubber bands for a speed and an optimum capacity. For fishing into holes, one needs sandows at the same time flexible and powerful to be able to draw with the first notch without failing and damaging the point,too.

Different sized guns have different uses;

60cm; For hole fishing, flatfish or very low visibility. Very manouverable, but with limited range. Some divers like to fit these with 5 pronger heads

75cm; The great allrounder, may be used for hole fishing or openwater. Short enough to be manouverable, with a lot more range than a 60. An ideal first speargun size.

90cm; More range than a 75, but a bit long for hole fishing. A good all round open water gun, particularly in the Southwest. My personal favourite

100cm; Useful for spooky fish in clear water. Normally only used in 30ft plus visibility. The extra 10cm of length over a 90 makes a big difference to range and manouverability

120cm;The South African standard. Very rarely used in the UK, as seeing the end of it can be a problem! Perfect for tropical reef hunting, with enough range for open water gamefish

140cm; Blue water special. For open water tropical gamefish The sizes of rubber powered spearguns refer to barrel length only.

The standard spear lengths for these guns are;

60cm gun; 100cm spear

75cm gun; 115cm spear

90cm gun; 130cm spear

100cm gun; 140cm spear

120cm gun; 160cm spear

140cm gun; 180cm spear

On Selecting A Speargun
This type of gun question is probably the most contentious topic in all of spearfishing and will continue to rage so as long as there are still fish in the sea.

The answer is largely dependent on a number of variables that change according to circumstance: the species of fish being hunted, the diving conditions (visibility, currents, and size of surf), the location being dived, and the experience of the diver. Accordingly, most experienced divers tend to own a collection of guns to provide them with the optimal tools in all conditions.

Having said this, most divers have a favourite gun that they use 80% of the time. This is especially true for divers operating out of their home water where conditions will be reasonably consistent, and where one gun will suffice for all but exceptional conditions. If you are unsure about selecting a gun, and have inquiries regarding the aspects of particular guns, please let us know.

On selecting spears:
The key to selecting a spear (and indeed to selecting any diving gear) is to always match the tool to the job at hand. No single tool is best for all jobs, they each have their specific pros and cons, and no single spear is the best for all hunting environments.

The key to a successful dive is to match the gun to the dive, and then select the correct spear to match the gun. So the spear you select will be determined by the gun you are using.

Spear Thickness:
The thickness of the spear will be determined by the rubbers. If you are using a multi-rubber gun, or heavy rubbers, we recommend that you select a heavier spear, in the 7mm to 7.5mm range. The reason for this is that a heavier spear will have more momentum (kinetic energy), and will go deeper into a large fish than a thin spear will. It will also be stronger so less likely to bend at impact, and will be stronger as you battle the fish to the surface, and less likely to tear out because the spear-barb is larger. But the most important reason for correct spear selection is that the spear will fundamentally determine accuracy. If your spear is too light for the rubbers, the gun will become inaccurate. The reason for this is that at the moment of release, the spear will bend slightly and start vibrating as it screams down the barrel towards the target, developing a slight U-bend. (You should visualize this as the back of the spear trying to catch up with the front of the spear). This phenomenon is called spear-whip and the next result is that the spear will not fly true, and the gun will usually shoot low. This is one of the major reasons why over-powered guns are inaccurate, but there are many others.

Spear Length:
The length of the spear will be determined by the length of your gun. Clearly a longer gun requires a longer spear, allowing you to get more range and stopping power. The support given by railguns allows the guns to use a shorter spear than a normal gun. The benefit of having a shorter spear is that the gun is more maneuverable, and the spear is stiffer and less likely to bend, but these effects are marginal in shorter guns. To make a standard gun accurate, the length of spear has to be such that the section protruding from the muzzle will counter the sag in the middle section, such at the moment of release the spear is straight and in the correct horizontal plane. The effect of having an overly short spear will be apparent, because the gun will shoot high. The opposite is true if too long a spear is used, as the gun will shoot low. The reason for this is that in a standard gun the spear is only supported in the mechanism and in the muzzle, while in a railgun the entire spear is supported.

In general, we recommend the following general configurations for our railguns:

The rule of thumb is that spears should be 40 cm longer than the barrel length For example, a 120cm gun needs a 160cm spear.
For guns up to 130 cm we recommend a 7mm spear. However, for guns longer than this, we recommend a 7.5mm spear.
Spear Composition:
Another major consideration when selecting spears are stiffness and corrosion. Spear bending is primary a function of the material the spear is made out of, and the length of the spear. The tougher the material, the less it will bend.

Straightening a spear is a non trivial process, and involves hitting and repeatedly rolling the spear on an anvil, so it is often better to get a stronger spear that is less likely to bend than spending a lot of time hammering away in your garage when you could be diving.

Spear Gun Safety:
Never load your speargun out of the water for any reason whatsoever.
Never fire your spear gun out of the water. The spear may break the shooting line, whiplash dangerously around, or may bounce-back at you.
Never point your speargun at anyone at anytime. While we make best efforts to make our safety-catches as robust as possible, if the gun is aggressively jarred there is the potential for an unexpected discharge. So always handle your speargun as if it were loaded and ready to fire. And always keep the spear tip pointed away from your body and away from other divers.
Always put the safety "ON" before loading your spear gun.
Do not swim with a loaded speargun through heavy surf. Rather load your gun once you have got past the backline.
Always unload a speargun under the water before removing it from the water, Never pass a loaded speargun onto or off of a dive-boat.
When loading your speargun make sure that the handle is securely positioned against your chest, with the spear tip pointed as far away from you as is possible. The number one cause of spear gun injuries occurs when loading guns, particularly large guns with more than one set of rubbers.
Always look behind what you are shooting at, particularly in bad viz. A rock might cause the spear shaft to bounce back at you, or another diver may have drifted behind your intended target.
It's very tempting to shoot at fish that have been attracted by the fish your partner has just speared. Most pelagics are curious and school around the struggling fish, providing attractive targets. So be doubly careful in these circumstances.
Always anticipate recoil. A large speargun is capable of removing teeth, smashing face masks, and breaking noses if not firmly held while firing.
Never modify or change the operation of your speargun by permanently disabling the safety or interfering with the firing mechanism.
Always secure your speargun in the boat and store it pointing towards the back of the boat.
Always keep the spear rubber on the tips especially when children are near and particularly when spears have been recently sharpened.

Speargun Maintenance:
Always rinse your speargun in fresh water after each use and allow it to dry fully in the shade before storage.
It often helps to give the handle a few good knocks with an open hand to help jar any sand that has collected in the handle out of the trigger mechanism.
For top performance, always inspect your speargun rubbers for wear and tear. We recommend replacing rubbers at least once every diving season. We also recommend that you check your wishbones prior to getting on the boat. Few things can be as frustrating as having a wishbone break and not having a handy replacement.
Store your speargun in a dry cool place.
All speargun shafts and mechanism should be lightly oiled periodically.
From: speartech