This mini is tested remotely up to 3x, and after manymanymany tests I have decided it is safe to be handheld with a 2x mix. It uses a simple BBQ ignition, direct propane, and a 3/4" sch80 union with milk-jug burst discs. The chamber is 6" of 2" sch80 and the barrel is 3' of 3/4" sch40. While the fittings arent sch80, they are NSF-pw, so for 2x mixes its fine.

This shot is a close up of the side of the mini, showing the propane system, union, and a piece of the foxtail ammo at the bottom

Here's the back of the mini hybrid. In this shot you can see the schrader valve.

This is the Foxtail ammo I use for testing. Its very simple, just a wrapped up shop rag with tape and a penny (for weight) on one end. Its lightweight and is extremely durable, so for testing purposes its ideal. Moreover, it slows down quickly, so it can be easily retrieved (not to mention it is a safe suburban ammo).