In my opinion, Velocity is all about pressures. However, you don't necessarily have to be in an overpressure situation to have a higher velocity. I feel like fast powders tend to give a fast pressure peak. Slow powders have a steady increase and get more efficiency out of their energy. It's like comparing a Diesel to a gas engine. A Diesel engine's fuel is burned in a constant Pressure while a gasoline is burned in a constant Volume. When ignition in a gasoline engine occurs the pressure on the piston is pretty instant. In a Diesel when ignition occurs the flame front is sustained nearly all the way past the mid point of the stroke because the injection of the fuel is over a longer period of time than an electrical spark from a plug and with gasoline's properties it explodes rather than burns. That's why all things being equal a Diesel gives a much better torque curve than a gasoline engine. If all the fuel is burned at the top of the stroke, the power surge is akin to hitting the piston on top with a sledge hammer. However, if your power surge is controlled by the fuel entering the cylinder and it continues well down through the power stroke, you will get a much steadier surge of power, or if you will, Push on top of the piston giving you more usable torque. Same thing with a bullet in a gun barrel. A steadier push is more efficient.
Last edited by Filaman; 02/17/19.
