Why can't bullets shot by high-speed cameras be regarded as particles when they pass through playing cards?

Because particles refer to points that highlight the mass of an object regardless of its shape and volume, they have no influence on the experiment, so they can be called particles. Bullets have their own length when they pass through poker, and the head and tail cannot pass through at the same time. Is specialized in studying this thing (high-speed camera), so we can't ignore the factors of shape and volume, so we can't regard it as a particle.