Projectile entry angle determination

Small angles of projectile entry are difficult to determine in two-dimensional targets or in three-dimensional targets where internal deflection has taken place. This results from the fact that small errors in measurement lead to large errors in the calculation of the sine function used in the estimation of the angular projection of a circle onto an inclined plane at angles of less than 20 degrees from the normal. The use of a bullet tip scale, constructed to the dimensions of the entering projectile, allows a significantly more accurate determination of small angles of entry in targets not subject to stretching. A comparison of the relative error inherent in calculating entry angle using the sine function and measuring the angle using the bullet tip scale demonstrates the suitability of using the tip scale at angles less than 20 degrees and the sine function at entry angles greater than 20 degrees.