There are countless options for different spear shafts. Some options you have control over, like shaft thickness, length and whether it is a threaded or flopper shaft. Spearguns limit what types of spears need to be used. For example, if you have a Euro speargun, you have little choice other than to use a Euro notched (rounded) shaft. Conversely American style spearguns require American notched (square) shafts. We will be going over some considerations in the factors we can control in the choice of our spear shafts. Shaft thickness is usually a consideration based on species and number of bands.
Thicker spear shafts help land larger blue water species, especially tough-skinned species like tuna and marlin. Thick shafts create more force due to their increased weight compared to thinner spear shafts. Thicker spear shafts also are less prone to bending under strain. Thicker spear shafts tend to be 8mm for Euro spear shafts and 11/32 or 3/8-inch for American spear shafts. The thicker the spear shaft, the heavier it is and the more force it takes to launch it through the water. Spearguns need to be larger to absorb the force of larger spear shafts.
Thinner spear shafts are lighter weight and tend to shoot further and penetrate fish easier. They are also more prone to getting bent by fish, especially large reef fish pulling them into rocks. Thinner spear shaft lengths tend to be 6.5mm, 7mm, or 9/32-inch shafts. Although 7.5mm and 5/16-inch spear shafts are still in the normal range of shafts used under normal reef hunting conditions.
Speargun length determines spear shaft length. It is important to try to keep the shaft overhang of your spear shaft consistent across all of your spearguns to help keep your point of aim consistent. Most manufacturers recommend between 9 and 11 inches of shaft overhang from the end of the speargun to the tip of the spear, whether it is flopper or slip tip. It is important to consider the length of slip tips in the choice and purchase of different spear shafts. This means that a threaded shaft will need to be shorter than a flopper shaft for the same speargun. Often times, manufactures will have recommended lengths for the specific speargun in various set ups.
Deciding between flopper and threaded shafts is based on targeted species. Pelagic or blue water species often require slip tips. Flopper shafts tend to work better on reef fish, because slip tips tend to give reef fish too much mobility to get into the rocks, which makes retrieval especially difficult.
Keep spare shafts for your spearguns in stock. It is upsetting to be invited out on a dive trip only to realize your only spear shaft is bent. Remember, overnight shipping is extremely expensive. It is always better to be prepared than to literally pay for a lack of being ready to dive.