Originally Posted by uv_halo
That's a given since, that's what Hydrotec is claiming, and it would be the most likely reason why they are more efficient and, why they will slow down faster.
I think it's much more likely that PistolPete didn't account for the HydroTec paint being a much bigger bore size than most paint out there right now. The weight may play a part, sure, but velocity swings like that should be expected if you're going from .680 and below to a stated .686. Since he's using an open bolt gun, maybe he didn't notice.