I have had some emails/pms asking about building a spear channel into the stock rather than using the spear guides I described above.
I designed this gun with guides as you can build it without having a router. But if you do have a router, a spear channel is probably better, and easier to load.
Basically, when you build the gun, you can use a hand held router to cut a spear channel down the centre of the stock. The channel extends between the shot engine (AKA trigger mechanism) and the muzzle. The spear sits in it. It stabilises the spear, making sighting and aiming more accurate, and it might reduce spear whip to some extent.
The spear needs to sit flat on the bottom of the channel, and also fit neatly into the shot engine. Fortunately, getting the correct levels for the two is not too complicated. You keep the top of the stock flat from where the shot engine is located to the muzzle. The shot engine sits in a mortise (hole) and has a flange near its top which determines how deep it is buried. I cut the spear channel between 3 and 4 millimetres deep, and about 7 mm wide.
If you follow these dimensions, the spear should sit nicely in the channel, and be a sliding fit into the shot engine.
To make the cut, I use a round ended 6 mm bit in the router, and adjust the fence so the bit sits just the tiniest amount to one side of centre, I rout the stock one way, then I take of the router, turn it around and rout the other side. To clean up the channel, I wrap a piece of sandpaper around a drill bit, and work this up and down the channel.
Sometimes, when you are in the water, it can get a bit fiddly fitting the spear into the shot engine, and getting the bridles engaging with the spear. This is especially true if you have thick gloves on. I find it a little easier to work the gun if I cut away a bit of wood for the 10 to 20 centimetres in front of the shot engine, cutting down to about 5 millimetres below the level of the top of the stock. This gives me extra room for my fingers
Ric Fallu started spearfishing in Pt Phillip in the early 1960s, and never really stopped