I couldn't find a thread specifically on the sgn-22 so I thought I'd start one. The sgn-22 is a single shot self ejecting design that I belive can be easily adapted to semiauto with a few changes. The bolt design my help those of us that want to make their own 22lr, 22mag, or 17hmr semiauto. While I don't think I'll make a sgn-22, I do think I may try making a 17hmr bolt for use in a standard ar15 upper with a 17hmr barrel using savage mags with an adaptor.
The first article basically listed the concept and showed the receiver construction which is basically a tube with a ejection port with a 10-22 barrel turned down to fit. Part two shows more of the bolt design which uses a modified ar15 firing pin and an ar15 type plunger ejector. It looks promising so far.