After many years away, I have recently gotten back into shooting clays. I used to shoot trap, but since then the idea of a "sporting clays" course has really taken off. With sporting clays you drive a golf cart from station to station or walk. The golf cart is fun, but the added cost wears on me. I saw a couple people on the course with modified baby jogging strollers and I thought, what a cool idea... but knew I could do better than that. So I had an idea and went searching the internet to see if anyone had beat me to it. I could not find one like this.
It is based on a Harbor Freight folding hand truck. Yes there are others made by Stanley and Milwaukee, but the Harbor Freight has better sized wheels (bigger). Some T hinges, 2" PVC, and a bit of woodworking on the shelf and I had a very usable gun cart. It folds up pretty flat but also holds everything securely while walking from station to station.
I was making one for me and one for a friend of mine that we go shooting with. His young son shoots a 410, he shoots a 12 ga, I shoot 16ga and my son 20ga. So I asked my son to design a 3D printable holder for a box of shells that could easily adjust to hold any of those sizes. He did a great job.
The maple shelf is finished with Milk Paint Co's Dark Tung Oil.
Source:
Harbor Freight Folding Gun Cart (more complete build details)
Shotgun shell box holder 3D model