What is Bore Line?

Bore Line refers to an imaginary straight line that extends from the center of the bore (interior of the barrel) of a firearm to infinity. In shooting and ballistics, the bore line serves as a reference point for aligning the sights or scope of a firearm with the intended target. It is crucial for understanding the relationship between the bore line, the line of sight, and the projectile's trajectory to accurately predict and adjust for bullet drop and wind drift.

Understanding Bore Line

When a projectile is fired, its trajectory is influenced by various factors, such as gravity, air resistance, and the rifling inside the barrel. The bore line represents the initial direction in which the projectile would travel in the absence of these external factors.

Some key concepts related to the bore line include:

• Line of Sight: The straight line from the shooter's eye, through the sights or scope, to the intended target. The line of sight is typically parallel to or slightly angled downward in relation to the bore line.
• Sight Height: The vertical distance between the bore line and the line of sight, which is the distance from the center of the bore to the center of the scope or sights.
• Zero Range: The distance at which the projectile's trajectory intersects the line of sight, resulting in the firearm being "zeroed" or "sighted in" for that specific distance.

Bore Line in Ballistic Calculations

Understanding the relationship between the bore line, line of sight, and the projectile's trajectory is essential for:

• Zeroing a Firearm: To zero a firearm, shooters adjust their sights or scope until the projectile's trajectory intersects the line of sight at the desired distance. This process compensates for bullet drop and ensures accurate shot placement at the zeroed range.
• Trajectory Analysis: Ballistic software and apps, such as Applied Ballistics, Hornady 4DOF, and Strelok Pro, use bore line, line of sight, and sight height data to calculate a projectile's trajectory, allowing shooters to make necessary adjustments for accurate shot placement at various ranges.
• Wind Drift Compensation: Knowing the relationship between the bore line and the projectile's trajectory helps shooters estimate and adjust for wind drift, improving accuracy in windy conditions.

References

• Litz, B. (2011). Applied Ballistics for Long Range Shooting. Applied Ballistics LLC.
• Barsness, J. (2006). The Big Book of Ballistics. Skyhorse Publishing.
• Cleckner, R. (2016). Long Range Shooting Handbook: A Beginner's Guide to Precision Rifle Shooting. CreateSpace Independent Publishing Platform.