Tried the 70 grain slugs sized to .2570 today and wow. Shot this 5 shot group at 50 yards. Refilled to 2700 psi each shot so cheated a little. Lubed with 10 wt silicon oil. Velocities I am now getting at about 3/8 power level are as follows:
986 fps
1001 fps
1002 fps
994 fps
986 fps.
Beginning pressure was 3000 psi and ending at 2500 psi. Started raining so had to quit. Group is about 3/8".