EP 146: The Riflemans Rule

Published on February 9, 2025
Duration: 1:27

This video explains the 'Rifleman's Rule' for calculating adjusted range in angled shooting scenarios. It highlights the inaccuracy of applying a cosine correction directly to the range, emphasizing that bullet drop is non-linear with range due to velocity loss. The speaker advises that this method becomes less accurate beyond 500 yards and 20 degrees of angle, leading to overcorrection and impacting low.

Quick Summary

The Rifleman's Rule, or horizontal range method, is used for angled shooting. However, applying a cosine correction directly to the range is inaccurate because bullet drop is non-linear with distance due to velocity loss. This method overcorrects beyond 500 yards and 20 degrees. The correct approach is to apply the cosine to the bullet drop amount, or use a ballistic rangefinder.

Chapters

  1. 00:00Introduction to the Rifleman's Role
  2. 00:02Geometry and Rangefinding
  3. 00:07Angle Measurement and Mill Relation Formula
  4. 00:12Cosine Correction for Range
  5. 00:18The Problem with Percentage Range Change
  6. 00:23Historical Ballistics Manuals
  7. 00:31Correct Angle Calculation: Bullet Drop vs. Range
  8. 00:40Linear vs. Non-Linear Drop
  9. 00:47Velocity Loss and Drop Rate
  10. 00:53Error from Applying Cosine to Range
  11. 01:00Limitations of the Rifleman's Rule (Distance & Angle)
  12. 01:05Alternative Names: Horizontal Range, Map Distance
  13. 01:11Impact of Overcorrection
  14. 01:17Correct Angle Compensation Methods
  15. 01:19Ballistic Rangefinders

Frequently Asked Questions

What is the Rifleman's Rule and why is it used in shooting?

The Rifleman's Rule, also known as the horizontal range method, is a technique used to adjust the effective range for bullet drop when shooting at an upward or downward angle. It aims to simplify calculations by finding the horizontal distance equivalent to the actual line-of-sight range.

Why is applying a cosine correction directly to the range inaccurate for angled shots?

Applying the cosine of the angle directly to the range is inaccurate because bullet drop is not linear with distance. As a bullet travels, it loses velocity, causing its drop rate to increase. This non-linearity means a simple range adjustment overcorrects for the angle, leading to shots impacting low.

At what distances and angles does the Rifleman's Rule become significantly inaccurate?

The Rifleman's Rule, when applied by adjusting the range directly, starts to become significantly inaccurate and lead to overcorrection beyond approximately 500 yards and at angles greater than 20 degrees. Beyond these parameters, the error in the calculation becomes more pronounced.

What is the correct way to compensate for bullet drop in angled shooting?

The correct method involves applying the cosine of the angle to the amount of bullet drop itself, rather than to the total range. This accounts for the non-linear nature of bullet drop. Alternatively, modern ballistic rangefinders can calculate this adjustment automatically.

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