On testing all, I used a standard WW2 Mauser 22 coil byf 9mm factory spring... It had about 4K rounds on it, and when I range tested Dick H.'s GTS/T-6, I ended up installing that exact spring in his frame, as I knew it worked with all the others, and it work with his as well.... (prior to that it wouldn't always close completely... It's a real balancing act when the barrels get fat!?....
... Best to all, til....lat'r..... GT