Muzzle velocity is essentially a random variable measured in conventional weapon testing domain, confidence interval and confidence level of muzzle velocity are calculated by firing a quantity of projectiles, as main equipment, accuracy of continuous wave Doppler is an important factor influencing quantity of projectiles used in test range. Muzzle velocity was evaluated in this paper, confidence interval and confidence level were calculated, and error of measurement of the radar was evaluated for velocity accuracy, the relation between quantity of projectiles and radar measurement accuracy was discussed in order to cut down consumption of projectiles, and increase efficiency of firing accuracy measurement, the minimum projectiles were fired for evaluating ammunition.