Abstract: The hydro-ballistic trajectory and cavity of the half sphere bullet and general pistol bullet are experimentally researched by a high speed digital video recorder when they entrain water at six speeds and at two depths of water. The experimental results show that the shape of a bullet has important influence upon the hydro-ballistics stability of the bullet motion. The hydro-ballistics of the half sphere bullet is stability, but the stability is not well for pistol bullet. The shape of pistol bullet cavity is “lotus root”. The velocity attenuation law of the bullet have similarity at a range of bullet entraining water speeds. The velocity attenuation law in water has similarity for both of the half sphere and pistol bullet. The speed of bullet in water decreases very quickly. A calculation model is established to predict the velocity attenuation law of the bullet. The calculation results are compared with the experimental results, they agree well with each other.

Key words: applied mechanics, water-entry, hydro-ballistics, cavity, experimental research, bullet