Ahh, I get you now.
Sorry, it's just that usually it'll be people asking to 'improve' their power by sticking a stronger spring in without doing anything else to it.
I'd try it on 0.43 or 45s and see what it comes out at, and then go from there.
Without knowing what's in it to start with, I can only guess at using something like an M140 or M130 to start with.
I'd also check the barrel is clean and bucking is in good condition before doing anything else.