If I were you, I'd order some 18# springs for your GC for hardball use. I think that you should be aware that the GC's have three problems----



1) The front sight is only staked in. You need to take it to a good smith to have it silver soldered in place so it won't fly off.



2) The rear sight is held in place by a roll pin. Replace it with a hardened steel solid pin for the same reason as above.



3) The chambers in GC's are tight. They're match chambers. Polish out the chamber about half a thou or so in order that any reload will chamber in it.



When I used to shoot at the Presidio, I had both my front and rear sight fly off at different matches. F.Bob Chow happened to see it happen to me and told me to take it to his shop the next morning and he would fix it for me. He did all of the above. Anyways, enjoy it as it is a target gun and if you keep hardball loads to a minimum, it'll stay tight for a long time to come. I used to use 3.5 gr of the old Hercules Bullseye with a 200 gr lead swc.