In case somebody wants some design files for a simple USPSA mini-popper....
The base is made from mild steel (a piece of laser-cut plate, some 3" equal angle, some 1" equal angle and some 2" flat bar). The popper plate itself is laser-cut from something hard enough for the job (VRN500, Hardox 500, or available equivalent).
The 3" angle protects the adjustment arrangement from being shot, but covers some of the popper plate. The size of the plate is thus designed so that the visible section (above the 3" angle when assembled) conforms to the USPSA rulebook size for a mini popper.
The files with extensions starting with "sld" are from SolidWorks - a free eDrawings viewer is available online.
Popper Assembly.pdf
Popper Assembly.sldasm
Popper Assembly.dxf
Popper Base.sldprt
Popper Plate.sldprt
3-8 in x 1.75 in Hex Bolt.sldprt
Popper Assembly.slddrw