Single stage? 2 Stage? I'd assume you'd call it a 2-stage... It's a military-style trigger with a secondary sear. All I know is GunDoc's trigger job is the standard Mini trigger, but MILES better.
AFAIK, he doesn't swap any parts in the trigger group -- he stones down the surfaces to give a shorter, smoother, lighter pull, and shortens the secondary sear spring a bit to compensate for the material that has been removed.
Hello: On semi auto rifles I'm having a hard time imagining a single stage trigger. That said, if the take up is minimized, clean, and the break clean and crisp, that is truly awesome! David the owner of Brimstone, started with 10-22's and built a deserved excellent reputation. I talked to him about expanding to Mini's because of their following being large and in need of trigger work. So mine was the first and it is perfect! He is cheap, quick, and very talented. If anyone here has used his services I'm sure they would say the same thing.
Good luck with your piece
I can't make a Mini trigger single stage due to it's design. The "single stage" in my trigger job refers more to how it feels. I adjust the factory parts (no new springs or screws stuck anywhere) so that it feels like one short, light pull rather that the two distinct weights you feel in the factory trigger. If you want to learn more about it I have a free video on my website that shows how it's done as well as some other Mini mods and maintenance videos. Admittedly the video is getting a little old, but except for a couple of differences I've made since it was uploaded years ago the trigger job is pretty much as shown. Even if you decide not use my services it's a good opportunity to learn how the trigger works and understand what can make it fail.