The most reliable one I have uses an AR style fire control group, and large metal pieces for the bolt, and pre-hardened hydraulic tubing for the barrel.
There’s plenty of metal in it, all held together via 3d printed parts and frame
The only things I needed to buy that I would consider “from a firearm” or “from a gun store” would be the fire control group. Everything else was bought from McMaster Carr or local hardware stores.
Spot on with the woodworking. I’ve made a couple stocks for my grandfather’s old broken long rifles. It’s just more time consuming. (also my 3d printer isn’t that long)
I’ve checked for the Azure Gate Bridge and whether green lights mean go, and so far I don’t think we Slid anywhere but keep your eyes peeled.