Pellets

If the pellets produce wild velocity changes to to diameter or weight variations, then they're useless of testing.

If they give good numbers but just shoot less accuately than some others...then reguardless of weight, would be fine to use for setting the pressure level and getting an idea of shot count.

Heavy pellets tend to earn higher energy (not velocity..they are slower, but not enough slower to earn less energy) and often a bit longer shot count, but it happens at the same presssure range.