I had the Madbull Ultimate hop up with the madbull blue bucking in there. I put in the PSG1 spring and that brought it up to 365 fps. I pulled that out and put the stock one back in with a G&G bucking. It's shooting a solid 400- 404 fps.
I'll try the O-ring stuff this weekend. I'm taking it to a game this weekend to try to stress test it sort of speak. Since I've just been testing it, I want to run a few mags through it and see if there's any change.