The relationship between the amount of powder and the resulting velocity of a bullet is not directly proportional. Simply increasing the amount of powder by a certain factor, such as four times, does not guarantee a corresponding increase in velocity by the same factor.
The velocity of a bullet is determined by various factors, including the characteristics of the firearm, the design of the bullet, the pressure generated in the chamber, and the efficiency of the propellant. Increasing the amount of powder can potentially generate more pressure in the chamber, leading to higher velocities, but it is not a linear relationship.
In reality, the relationship between powder charge and bullet velocity is complex and nonlinear. There are diminishing returns as the powder charge increases. This is due to factors like diminishing efficiency of the propellant burn, increased friction, and other limitations imposed by the firearm design and bullet characteristics.
Therefore, increasing the powder charge by four times would not necessarily result in a quadruple (four times) increase in bullet velocity. The actual increase would depend on multiple factors and may be less than four times, especially considering the practical limits and constraints of the firearm and ammunition design.