Pick a midweight pellet for starters, and check velocity in the middle of the sweet spot of the charge. If you are not sure where the sweet spot of the charge is, follow the procedure below:
1. Charge the gun to just over 1500psi and dryfire it once.
2. Now chronograph three shots and write the velocities down.
3. Dryfire ten times, and chrono the next three shots and write them down, along with the remaining gage pressure.
4. Again dryfire ten times and chrono three more and record velocity and remaining pressure.
5. Repeat the dryfire and crono operation UNTIL you reach the lowest velocity you plan to consider using.
Examine the results you have, looking for the highest velocity range pressure, which will be the middle of your "sweet spot". Check the energy level of those highest velocity shots, and, once recharging to the exact pressure you saw the peak and (go a little bit over and dryfire down to it), adjust via hammer spring preload if too high or low for HV class, ideally to around 19fpe for starters.
To find energy of a certain pellet at a certain velocity, multiply the pellet weight in grains times the velocity squared, then divide by 450,240 to arrive at the energy in foot pounds.
Once you know your peak velocity is adjusted so its near enough, but not over the max energy spec, shoot from the peak level over the chrono while counting shots until the average of three shots is unacceptably low, say 15fps slower than the peak and look at the precise pressure on the gage ... this is about where you need to stop and recharge. Generally, when recharging, you should go around 200psi higher than were the midpoint was or a bit less even, and recheck the velocity, with a goal of STARTING the charge around 15fps of less lower, then slowly climbing to the max velocity and then slowly dropping to the min recharge level. COUNT the shots for beginning to end, so you know how many sighters you can take and still have enough air for 25 good record shots.
NOW, and only now, should then test every type of .177 pellets to see which give the very best accuracy (ideally both indoors and outdoors). Shoot all the pellet types you have at or near that peak pressure level to see which are most promising accuracy wise.
