Spearfishing Muzzle

07/22

Muzzle (n.) - the front end of a speargun which holds the track for the spear shaft as well as a hole for the bands. This is often the limiting factor for a gun's accuracy and plays a large part in it's look and feel.

This goal with this project was to improve the performance and shooting precision of my speargun while maintaining a similar aesthetic. My speargun came stock with a closed muzzle design which keeps the spear shaft contained within a plastic arch but allows for quite a bit of play. This design is good for beginners because it is easy to rig, but it is imprecise in the water. My idea was to redesign the muzzle with an open track, utilizing the shooting line to constrain the shaft for minimal play. This design allows the speargun to be rigged quickly by simply wrapping the line around the hook. It also allows me to replace the fixed band with a loose band that can be easily replaced and tuned.

Completed muzzle printed with Markforged Onyx carbon reinforced nylon filament (initial PLA prototype lying in front)

Skills utilized:

  • CAD (Fusion 360)

  • 3D Printing (FDM - Markforged composite printing)

Stock muzzle design. Notable features include the plastic arch and fixed bands.

Design and Manufacturing

I took measurements around the key features and contours of the existing muzzle, then drew out a concept design. With a vision and numbers to work with, I was able to put together a CAD design in Fusion 360. I 3D printed this first using PLA and confirmed the sizing. I then made a few tweaks and printed it using Onyx filament on a Markforged 3D printer.

Another part of the manufacturing process was fabricating a new band (or rubber, the mechanism which propels the spear). These usually come pre-made when buying spearguns, but because I was customizing mine and ditching the old mechanism, I had to make my own. This challenged my knot tying skills, forcing me to learn a couple new techniques. They had to tied precisely because the anchors and line that connect the band support immense loads.