Мылтықшы ережесі: Еңіс бұрыштарда нысана алу тәсілі

Rifleman's rule is a "rule of thumb" that allows a rifleman to accurately fire a rifle that has been calibrated for horizontal targets at uphill or downhill targets. The rule says that only the horizontal range should be considered when adjusting a sight or performing hold over in order to account for bullet drop. Typically, the range of an elevated target is considered in terms of the slant range, incorporating both the horizontal distance and the elevation distance (possibly negative, i. e. downhill), as when a rangefinder is used to determine the distance to target. The slant range is not compatible with standard ballistics tables for estimating bullet drop. The Rifleman's rule provides an estimate of the horizontal range for engaging a target at a known slant range (the uphill or downhill distance from the rifle). For a bullet to strike a target at a slant range of and an incline of , the rifle sight must be adjusted as if the shooter were aiming at a horizontal target at a range of Figure 1 illustrates the shooting scenario. The rule holds for inclined and declined shooting (all angles measured with respect to horizontal). Very precise computer modeling and empirical evidence suggests that the rule does appear to work with reasonable accuracy in air and with both bullets and arrows.

There is a device that is mounted on the rifle called a sight. While there are many forms of rifle sight, they all permit the shooter to set the angle between the bore of the rifle and the line of sight (LOS) to the target. Figure 2 illustrates the relationship between the LOS and bore angle. This relationship between the LOS to the target and the bore angle is determined through a process called "zeroing." The bore angle is set to ensure that a bullet on a parabolic trajectory will intersect the LOS to the target at a specific range. A properly adjusted rifle barrel and sight are said to be "zeroed." Figure 3 illustrates how the LOS, bullet trajectory, and range are related.

This section provides a detailed derivation of the rifleman's rule.

Equation 6 can be obtained from the following equation, which was named equation 11 in the article Trajectory. This expression can be expanded using the double angle formula for the sine (see Trigonometric identity) and the definitions of tangent and cosine. Multiply the expression in the parentheses by the front trigonometric term. Extract the factor from the expression in parentheses. The expression inside the parentheses is in the form of a sine difference formula. Also, multiply the resulting expression by the factor
Factor the expression from the expression inside the parentheses. In addition, add and subtract the expression inside the parentheses. Let
Let (see Equation 1) and simplify the expression in parentheses. Expand
Distribute the factor through the expression. Factor out the and substitute
Factor out
Substitute into the equation. Substitute the definitions of , , and into the equation. This completes the derivation of the exact form of the rifleman's rule.