Thought I’d share one of my projects with you. It’s a 12gauge 2-3/4 Shot-Shell Caddy that holds 28. I have completed the first physical prototype for a concept test and working on a polymer design currently. Mounting is done with straps and Velcro on a belt or chest rig on the current prototype, next generation will be configurable.
Capacity: 28, 12g 2-3/4
Mounting Orientation: Any
Loading: By Hand
Unloading: Remove 2 or 4 simultaneously
Springs: Standard 30 round AR Magazine spring
Polymer is the intent with added internal geometry and reduced overall dimensions. I was able to do a job for some SS laser cut parts and used those for prototyping 4 complete units to test the concept, next step is 3D printing. In the end injection molding would be best for production and added strength. 3D printing even with the same polymers is typically weaker especially between the print layers.
Injection molding would be the way to do it but the mold cost alone is hard to justify unless you predicted sales volume is thousands a year. You look like you know your way around metal… Have you researched doing it out of tig welded aluminum plate?
It is very doable in steel and aluminum. Plate if milled with the added geometry could be utilized; however, at much added cost and a multiparty assembly. Stamping would be lighter and likely stronger, but requires stamping dies and fastening including tig, spot, riveting, etc. For a large section an AL extrusion can be used at a much lower cost once a volume was achieved. Extrusion dies cost a few thousand and generally have minimum quantities to extrude. The other pieces at that point could be machined, stamped and molded at a lower cost. From an end product standpoint injection molded would be best for both price and performance; however, economy of scale plays a large factor as you stated.
A few challenges are presented if using sheet metal for the fabrication of the feed lip area, this sheet can be hard on your fingers even after rounding and sanding due to the thickness and resulting pressure (force/small area). This section for comfort must have enough thickness to smooth the radii and decrease the overall pressure when sliding out the shells. The current sheet steel prototypes can be a bit rough at .065" thickness.
Second is spring pressure, fully loaded pressure can be high using commonly available components such as 30 round magazine springs. Two rounds can be stripped out quite easily while 4 rounds presents a challenge currently. I have a few adjustments to make to ease this effort.
Thank you for the feedback and interest, it’s appreciated
A problem that you’ll run into for quad loading is that you can’t get your fingers wrapped around the shells for the initial “pluck”. Looks like you won’t have a solid grip on them when they’re released and the fumbling will offset any speed you’ve gained by loading quads.
You are correct that it is an issue. Stripping/rolling out two is very easy, but not quad load. Quad load is a bit trickier and space can be a problem compared with the existing caddies. I’ve been playing with the technique and some geometry that has helped out, but fighting spring tension is a thing when fully loaded. A different spring could be used to give a “constant” tension to reduce the load. Three base issues is the shells have a separation between them when plucked and not tight, the spreading of fingers and curl will aggravate carpel tunnel, and as stated slightly out of position for the quad load method. If you like having a ton of ammo accessible on a belt/rig for field use I think this is a win, competition use not so much.
