A good way to find the load is to do a ladder load. Start with your current carge as a middle, and go like this
21.0, 21.3, 21.6, 21.9, 22.2, 22.5 and on and on. I usualy end up with 18 rounds to test, all with .3 grain diffrence. Sarpie the charge, and shot number on the casing to keep track of them. When you shoot fire one round, mark it wit the number, and fire another, keep going up the ladder till you start to see signs of excess pressure, thats where you stop. You should end up with a vertical string of numbered shots. What you are looking for is the highest grouping. That puts your