A How to Guide on Proper Internal Ballasting of a Custom Built Speargun
The proper way to ballast your own speargun is critical in the final functionality of your speargun. It impacts the balance, recoil, and buoyancy of the gun. A properly ballasted speargun is one of the most under-rated pieces of gear a spearfisherman can have.
The proper method of ballasting requires a body of water with the same approximate salinity you will be using the speargun. If you will be spearfishing in the ocean take your mostly complete speargun to a nearby boat dock. The tools you will also need are some lead weights and some tape.
You want the speargun to be as similar at this test stage to how it will be in the water. You will need your spear in the gun and bands to load for this test. Set the gun in the water to see how the gun sit is the water. Once you have an idea of how the gun sits in the water you should start taping small amounts of lead to the gun. Adjust the position and amount of lead on the gun until it sits level and is slightly negatively buoyant.
After you know how much lead you need you can use our calculations to determine the slot you will need to make. DO NOT POUR MOLTEN LEAD INTO YOUR ACTUAL SPEARGUN! Use a cheap piece of wood to pour the lead. Once the lead is cooled you can put the lead into the slot you have routered on your speargun.
Once your speargun has the block of lead in it you can mix a small batch of epoxy with pigment mixed in. Pour the epoxy to secure the lead and ensure proper ballasting.
For router table safety check out this site.
For external ballasting see the OctoSub Speargun Ballast Kit
The below video is a step by step guide to ballasting a speargun using Neptonics components.