You need 2 "perfect pellets" for any gun

You shoot with the most accurate, because if you can't hit the target nothing else matters,
but you chrono to stay legal (sub 12) and you do that with the pellet which gives you the highest muzzle energy, because you need to be legal with any pellet not just the one that your barrel happens to prefer.

If you use a V frame chrono you can use it at the muzzle or out at the target if you want to, many other types can only be used at the muzzle.
My choice is a pro-chrono digital.