smotrs, the 'secondary impulse' thing is nonsense but the advice to use minimum tension is sound. Moreover, your practice of using a bowline is acceptable. There is another knot similar to the bowline and is smaller but I don't know how to explain it. Otherwise, the subject of stringing a gun is fairly complex, you may have gotten a sense of that from the previous posts. Actually, I know spearos who have spent considerable time rigging and rerigging guns with complex and tricky arrangements for specific types of diving and for specific game. I assume that you are a scuba diver and don't plan to use a reel. I assume that your Biller gun is mahogany (floats higher than teak and has less inertia than teak). Anyway, you should think about getting rid of the shock cord if you intend to load your gun heavily. If not, if you use light rubber traction, the cord should be OK. On big Sea Hornets the shock cord will cause the shooting line to throw loops and sometimes will loop over the rubbers binding everything. It will prevent a reel from deploying if one is used. I'm enclosing a short article I wrote on rigging the Sea Hornet (Biller)
*The Sea Hornet is a rubber band spear gun with wood stock, plastic muzzle, grip and butt. Firing mechanism is "drop" type made of stainless steel. Originated in Australia, the gun is sold in the US by AB Biller.
The Billers are Austrian immigrants who are not just marketers, they are craftsmen and machinists who have over the years, made extensive
modifications to the Sea Hornet concept. One of the first innovations was the introduction of 17/4 ph SS shafts as standard equipment. Since then, they have offered a selection of high grade woods while eliminating certain weaknesses in the overall gun. New plastic parts have thicker walls than the original gun. The wooden barrels are thicker and offer a much stronger lockup and fit. The new grip and muzzle are cast in such a way that the shaft is now correctly aligned in the barrel groove offering better accuracy. Changes, mostly beneficial have been made to the trigger sear and line release.
These changes make the gun suitable for the average diver. However, specialists, such as freedivers may want to consider the following.
Selection of woods depends on the size of game. For guns 48" and less, mahogany is the best choice. This wood is light and strong and does not
react to seawater. It should be coated with a lacquer, however, and this is standard. Because of the relative lightness, the gun floats well, even with a reel attached. Also, because of the low weight, the gun has low "inertia" and tends to jump a bit when heavy traction is used. The teak barrels are recommended with larger guns(54"). The extra wood length provides (barely) adequate flotation, but more importantly the weight means high inertia and improved accuracy with HEAVY traction. The wood is stable in seawater but should be coated with "Tiptop Teak", a special oil.
The ideal reel to use is the aluminum trigger type reel with drag. This reel is sold by Bandito and was designed by J. Riffe back in the 60's.
It holds over 100 feet of line. The reel's trigger is used to "snub" big fish before they can dive into a wreck or rocks. The line itself should be 1/8 soft nylon with a swivel connection to the shooting line. This line should be 1/16", 49 strand, SS cable. Cable is not as dangerous as might be expected. Loose cable sinks away from the diver. Cable is more hazardous to tank divers than freedivers because large fish may try to "wrap up" the diver and his gun. In either case, I recommend cable.
The stock rubbers and wishbones are OK, but I do not recommend. I do recommend that the excellent Biller black coated amber rubber be used, either 9/16 or 5/8, depending on power requirement. Black coated rubber must be used since it does not spook fish the way amber rubber does. Solid black rubber should not be considered. I make wishbones from 3/32" 19 STRAND cable. The ends of the wishbone are common electrical solder cast on the ends, 5/16 dia. using a special flux.
The spear tip is a handmade sliptip, 4 1/2" long. It has two flukes which are set in THE SAME PLANE as the line hole. The tip material is 17/4 SS, in 3/8 hexagonal. The tip is attached with nylon line. Shoulders are ground forward of the line hole to protect the line(hard layed 1/8" nylon). Line is used to avoid tearing the fish during battle.
The spear is a special order from Biller without wishbone grooves. A SS "rudder" is fabricated and TIG welded to the shaft in lieu of the
wishbone grooves and line stop. The Biller slide rings are discarded and replace with a wound SPRING STEEL version from JBL.
The muzzle is cut back a little to allow for passage of the "rudder". Enough plastic should be left to capture the slide ring when the gun is
loaded.
Miscellaneous: no bungee cord is to be used, ever. With big guns, the recoil effect of these things cause to shooting line to spring back and throw loops, sometimes wrapping the muzzle and DISABLING the reel. Also, the knots used may reduce strength of the line.
If a trailing line is to be used the butt may be drilled up to 3/8" without affecting strength of the wood.
If the "Limited Edition" Sea Hornet is used, different mods are required.*
PS: smotrs, many freedivers and others do use shooting line rather than cable. A few even use thick monofilament. I don't recommend the mono. However, a comment about the line. This is a stiff type of nylon used by tuna long liners and is called 'tuna line'. The pros started using this back in the 60's. The normal size is 3/32", 350#. This line is too stiff to tie a good knot unless pliers are used, and is usually secured with brass sleeves (tackle shop) using a crimping tool. The tool is the type with a crescent and tooth arrangement, not the squeeze type used for steel cable. Lastly, there is kevlar line. This ultra thin line is good for shooting line but cannot be used on a reel due to binding and backlash. The whole point of a good shooting line is low drag. Kevlar is not only thin but wonderfully strong. It can be tied easily but the ends must be glued, not heated as with nylon. One drawback (?), it is not easy to make shock cord due to the thin dia but it can be done. Like all shock cords, tie two knots (figure 8 knots due to the cord's small dia) spaced slightly longer than the rubber tube. Pull the line and one knot into the tube. Tie off the knot end with thin nylon twine. Stretch the tube over the second knot causing the line to bunch inside. Tie off the second knot.
Pesky
