I'm glad you mentioned the Limb Saver deresonator, I saw that and it looks interesting. Glad to hear it helped you. I have a lot of respect for the Limb Saver folks.
As far as how much pressure to add, that will vary from one gun to the next. Try a little pressure, then try a bit more, and see what happens. Shoot the rifle each time you make a change in pressure so you can see just what effect your changes have had on accuracy.
Accurizing is funny... you have to try one thing at a time because you never know what one thing will improve accuracy. For instance, that Savage you rebarreled... you may have been ahead to rebarrel the action (getting the headspace just right with a gauge of course, which I hope you did), put it in the stock and go to the range. Then if it needed improvement, you could try glass bedding the action and go to the range again. If it still needed work, float the barrel (or whatever the next logical step may be).
It's almost as much an art as a science, because each rifle is an individual and has its own quirks. If you change more than one thing and it gets worse, then you will never know if just changing one thing might have fixed it. Conversely, if it gets better then you won't know which one of your steps was the one that caused the improvement.
Have you tried various ammo in your rifle? Some rifles will shoot one load poorly but another load will group nice and tight. Changing bullet weights, brands of ammo, etc, can sometimes make a big difference. My Savage 270 will shoot Winchester factory 150s pretty well, but it hates Remington 150s. Scatters them all over the paper. It comes back to each rifle being an individual. Finding the best load for your rifle is sometimes an aggravation, but if you are looking for good accuracy then it's worth the effort.
- Russ Chastain