Oops, almost forgot to try to answer your question.
Without more exact info, it sounds like your reloads are in the vicinity of around 750 f/s.
If so, you could probably get decent results with recoil springs anywhere from the stock one down to 14 lbs.
Maybe even a little less.
No telling until you try and see.
But if the gun is running well as is, it's always a good idea to quit while ahead.
Changing recoil springs can have many undesirable side effects with feeding, timing, point of impact changes, 'etc.
It's easy to forget that springs have effects in more than one direction.
