Objective To provide a mathematical formula and method for estimating the distance of shooting by uniform shotgun. Method 360 distribution graphs of canister were made on experimental target paper by shooting with No. 12 and No. 16 uniform shotgun (made in China), using No. 1 and No.3 pellets at the distance of shooting from 1m to 12m. The data of graph measuring and experimental distance were analyzed by mathematic theory. Results Six different types of mathematic formula were obtained for deduce the distance of shooting. They are: 12-1 type (choke) ss= -0.2 + 0.44d; 12- 1 type (no choke) ss= -0.94 + 0.63d; 12-3 type (choke) ss= -0.59 + 0.52d; 12-3 type (no choke) ss= -0.36 + 0.34d; 16-1 types= -0.37 + 0.30d; 16-3types= -0.16 + 0.23d. General software was made using Visual Basic 5.0 computer program. Conclusion This method can be used to deduce the distance of uniform shotgun shooting with little error.

Objective To discuss the condition in which ricochet bullet wound is formed, study its ballistic characters and ability to damage in the body, and establish features for the diagnosis of ricochet bullet wound. Method We shot four Yorkshire pigs by selecting No.54 pistol (made in China) and No.56 semiautomatic rifle with No.51 pistol bullet and No.56 rifle bullet, using quern stone as ricocheting target, copied 12 cases of ricochet bullet wound models and observed the characters of entrance wound, wound cavity and cartridge point. Results The formation of ricochet bullet lies with the properties of the target, the shape and velocity of the bullet, angle of incidence and angle of ricochet; the angle of ricochet formed by sharp bullet with high velocity is smaller than the angle by the round bullet with low velocity under the same circumstance; the wound does not produce an evident temporary cavity; six features for the diagnosis were established according to experimented results. Conclusion The correct diagnosis of ricochet bullet wound is of practical value to judging direction and distance of shot, trajectory reconstruction, analysing purpose of shot and evaluation of injury degree.