No, even if considering an ideal environment (no draggy airframe/engine, no air resistance) the theoretically calculated speed would be the best possible one.

From experience a very good speed setup reaches about 90% of the theoretical prop speed at given rpm (rpms of an unloaded engine during a powerdive derived from Doppler effect measurements).

Boundary conditions are:

- low drag airframe supporting the engine/prop combo to unload with ease after the first dive
- low drag speed prop designed for a certain rpm and target speed
- an engine swinging the prop within its highest efficiency
- preferably subsonic prop tip speeds
- speed measurements in both directions, headwind and downwind