Waterproof Sniper's Logbook

To use all the features of the measuring disc, put a 30-35 cm / 12"-14" shoelace or gutted 550 paracord in the origin point of the disc (yes, make a hole in the thing).

Wind speed

• Hold the disc arrow down and the disc to the wind
• The shoelace/paracord hangs free
• Read the wind speed from the disc at the shoelace/paracord angle

Cosine

• Hold the disc arrow down
• Aim at the target along the disc’s top edge
• Read the cosine multiplier from the disc at the shoelace/paracord
• Cosine multiplier x actual target distance from muzzle = effective distance
• E.g. if a target is 300 meters from your muzzle, but a 100 meters higher from sea level, the effective target distance you use to adjust your elevation is 283 meters
• This is due to gravity working only in the direction of Earth’s center mass
• So to recap: Shooting at an upward or downward angle, the ballistic elevation correction is always smaller than when shooting horizontally at the same target distance

Effective crosswind

• Hold the disc face up and arrow toward the target
• Have wind speed and angle ready
• Choose wind speed from the bottom row 1-10 (the speed unit doesn’t matter)
• Move up along the arc until you reach the wind angle line
• Go straight down to the bottom row, and read the effective crosswind speed
• E.g. 4 m/s wind at a 30 degree angle will yield a 2 m/s effective crosswind

The visible size of objects at an angle

• Hold the disc face up and arrow toward the target
• Imagine the object’s angle on the disc
• Choose the actual target size from the bottom row (e.g. 6.0)
• Move up along the arc until you reach the angle line
• Go straight down to the bottom row, and read the apparent target size
• If a 600 mm wide object is at a 30 degree angle (90 degrees means facing you), it will appear as 300 mm wide
• So: If an object you know to be 600 mm wide and at a 30 degree angle, and it measures at 1.0 MRAD wide on your optic’s reticle, it is 300 meters away
• Simple math!

Instructional video

This video shows the use of a similar measuring disc. The video is in Finnish with no subtitles, but you will get the general idea of how to operate the various features of the disc. The logbook shown in the video is also a Finnish language version not available in our store.