...my GSG included.
Changed out trigger,msh, grip safety, hammer, guide rod, bushing, thumb safety, grips, sear and disconnector.
Trigger job (of course) for 4# pull and made a solid brass guide rod and steel plunger tube. I always questioned the idea of separating the sights from the barrel so I made a compensator (or two

) and fitted the barrel properly to the bushing. Tossed the barrel screw in the frame and improved the accuracy a BUNCH.
A few cosmetic changes, removed the billboards on the slide, flattened the top and duracoated the rascal making it plain and simple.
Grips, I grabbed a take off pair from my RIA .38 super, wiped everything down and shoot the hell out of it.
Some folk like a lighter pistol but I found the weight of the GSG lacking. That is why I used brass and steel tor the parts I made for the front of the piece. Aluminum or another light alloy will work as well if one wants the lighter feel.
I would warn GSG owners that what I have done will absolutely void any warranty and should not be done without serious thought.
SUPPORT YOUR LOCAL GUNSMITH!
I work on MY guns because I can but I am NOT a gunsmith. Proceed at your own abilities and risk. PLEASE BE CAREFUL! Have fun, shoot straight.
Photo(s) follow.
Slim