Modifying a speargun

Care is needed to determine design objectives before undertaking modifications. It’s also important to predict what might be lost, as well as what might be gained.
This vid is about upgrading a light euro gun to something more suitable for slightly larger fish.

[@diyspeargunner2386]

Erratum : I said the gun was initially built in 2006 : that was wrong, it was in 2010

[@thekingpotato8214]

cant wait to see you with the dentex

[@diyspeargunner2386]

I’m looking forward hopefully. But ATM it’s a three year program : a trip to the Mediterranean this northern summer (as much to escape the southern winter as anything, but I want to work out the lay of the land, the more serious subsequent trips. All the while working on my deeper diving and breathhold skills

[@diyspeargunner2386]

For those who don’t speak English, I attach written text you can translate via Google, or other means “Spearguns are trade-offs when it comes to design What you gain on the slides you’ll most likely lose on the seesaws You have to be careful with how you modify, or you may compromise the function of what was a good speargun. I don’t usually modify spearguns. I find it cleaner and neater to build a new one. But this once, I thought I might try to upgrade and oldy and a goody Back in 2006, I built what was a light Euro pipe gun, but made from wood. The goal at the time was to make a speargun suitable for taking pinky snapper in Melbourne’s Port Phillip Bay. I wanted something very accurate but manoeuvrable enough to track the pinkies as they ducked and weaved The stock was minimalist, reducing water resistance. The spear was narrow, 1/4 inch in diameter, making the gun easy to swing, and, once the spear was launched, the spear flew fast. With the co-planar rubbers and elevated handle position, the forces were aligned, resulting in very accurate spear flight It’s been one of my more successful builds. Since I made it, it’s accounted for hundreds of pinky snapper, quite a few flatheads, some King George whiting and sundry other species. Its narrow body is really easy to push through the water, allowing more time in the kill zone. There’s no doubt the design has been fit for purpose. But I decided I wanted to change the design a little. I’ve set myself a goal of going to the Mediterranean and shooting a three kilogram dentex Some people may think this a bit ambitious for someone at my skill level, but let an old man have his dreams. I need the gun to be better suited to take the similar, but larger and stronger fish. Hopefully the modifications will make it fit for the new purpose. The first modification will be to change the spear to 7mm diameter. The heavier spear should have more range, better penetration through fish flesh, and be less likely to be bent by a struggling fish But it will mean a heavier gun with increased recoil, and the spear will fly slower. I’ll put in a shorter spear, which should reduce the weight a little. The trade-off for the shorter spear is the front overhang may reduce aiming accuracy a little. Perhaps. Maybe. Whatever, I’ll just have to live with it. The gun has a closed muzzle : there is just enough room for the 1/4 inch spear and the monofilament shooting line to pass through. I’m a bit worried that a fatter spear might jam, so I’ll get rid of the thicker mono shooting line, and replace it with a thinner one, giving just a little extra clearance. The thinner mono should be strong enough, and it might let the spear fly just a little faster. Tying a float cord to the gun decreases manoeuvrability (and this applies to both tethering and breakaway rigs) Historically my preference has been to use a drop rig. This has been my practice for Port Phillip snapper, and I suspect it will remain true for Dentex in the Mediterranean. I think it’s best to let the fish run, and exhaust its energy, before pulling it in. So you may need to drop the gun after the shot, and retrieve it later. But the Mediterranean can be deep. I decided to add a reel, as is common practice in the Mediterranean. I generally don’t like reels : they can spool (jam) when under tension, and they make the gun more bulky. But I did a search and found that there are some quite small reels Kind of cute I think. Anyway, I want to use the reel as a fish finding device, not as an aid to fighting a big fish, so the reel doesn’t have to be big and it should be less likely to spool. The scenario I dream of is to hit my three kilogram dentex, and let it swim off with the spear while I head for the surface, unspooling as I go. After I’ve got my breath, and allowed time for the fish’s first burst of adrenaline to dissipate, I can use the reel line to find where my quarry has holed-up in the rocks. To fit this gun, the reel needed a base. and I had to chop a mortise and inset a base into the gun. The previous set of rubbers pushed the 1/4 inch spear pretty well, but more power might be needed for the heavier spear. If I find it needs more power, I plan to replace the existing rubbers with shorter progressive rubbers. Will it work? I hope so. The theory seems sound, but the only real way will be to use it in the water.”

[@diyspeargunner2386]

My original description for the gun was given at kzbin.info/www/bejne/Y6CbiJVvf75peMUsi=0u85RT_lKVbD3xft