Manual ballistics - UNITAF Force Manual (FM)


Group

Manual ballistics
This group is not in a published chapter and should not be relied upon.



Guide
FM/BG-452 - Using a rangecard
Guide

The range card, common to all marksmanship roles, provides ready access to some of the most frequently required information for placing measured shots at distance. The first and largest variable to account for in all ballistic solutions is bullet drop, or the effect of gravity on a bullet in flight over time. Autopopulated for your unique combination of rifle and optic in hand, the range card dedicates a majority of its data to accurately accommodating this first variable in a ballistic solution.

 

The colored columns under the range card’s “Bullet Drop” section display different sets of adjustments to accommodate the effects of temperature on bullet drop. As temperature affects both muzzle velocity and air resistance, the differences between cold and warm climates can have a significant effect on how far a bullet will fall due to gravity at any given range. Be sure to have a rough estimate of the temperature in hand to help decide which temperature column to read.

 

With an appropriate temperature column picked out, all of the below values will display how far your bullet will drop for the given “Target Range”, found on the far left side of the sheet. These drop values are measured in milliradians, or MRAD. For example, a value of “-4.5” (reading the 15°C temperature column at a distance of 500m) describes that your bullet will fall 4.5 milliradians below your crosshairs at that distance. To counteract that negative drop value, we need to either hold the crosshairs 4.5 MRADs above the target, or dial our scope up 4.5 MRADs to bring the bullet impact back up to our crosshair level.

 

In a similar fashion, the range card also provides information for use with wind accommodation, engaging moving targets, and for calculations requiring general equipment information. This data, however, is seldom required in the opening marksmanship roles where simplicity encourages speed, and speed is our most valuable asset.

 

At the highest level of marksmanship roles, it should be noted that the populated BDA information is limited to temperature and equipment considerations only. Displayed drop values do not account for changes in altitude, pressure or humidity variables, as default Arma values are assumed. This under extreme conditions may compromise all drop, wind and moving target information, requiring manual data collection or calculation.

Skill
FM/BS-429 - Manually adjust for bullet drop using a range card
Skill
  • Look up the vertical deviation caused by gravity using the range to target and a range card
  • Integrate the calculated value into the final ballistics solution
Skill
FM/BS-413 - Manually calculate and adjust for wind
Skill
  • Calculate the horizontal deviation caused by the wind using the Beaufort scale and range card values or comparable methods
  • Integrate the calculated value into the final ballistics solution
Guide
FM/BG-454 - Horizontal Coriolis Force: Introduction
Guide

On its path around the Sun, our planet rotates around its axis at a staggeringly fast constant speed - and all things in contact with the planet spin along with it. A vehicle in motion, a cyclist at rest, even a rooted tree all spin along with the planet as they are in direct contact with the Earth. When an object separates from the planet, such as a ball being tossed into the air, this inherited rotational velocity gradually begins to decrease as the object in flight is no longer being propelled by contact with the spinning Earth. As observed from our constantly rotating rifles, this gradual loss of rotational velocity shows itself when a bullet in flight begins to rotate around the earth slower than our scopes and appear to drift to the left or right on its way to the target. We call this relative motion the Coriolis effect.

 

Both the direction and the magnitude of horizontal Coriolis deflection will change according to global position. As we move closer to either the North or South pole (as latitude increases), horizontal Coriolis deflection will also increase, with the most extreme effect being observed directly on either geographic pole. As we move away from the poles and towards the equator (as latitude decreases), horizontal deflection also decreases, with horizontal Coriolis deflection being entirely absent directly over the equator. Direction of deflection is dependent on which hemisphere a projectile is in, deflecting to right in the northern hemisphere and to the left in the southern.

 

[picture]

 

The Coriolis effect produces a relatively small effect on our bullets’ trajectory when compared to primary variables such as bullet drop and wind. In the opening applications of marksmanship where speed is key, Coriolis deflection is well accounted for by a fast and measured follow up shot in response to any misses. In more advanced applications of marksmanship, where precision becomes precedent and greater ranges more common, Coriolis will become a key variable to factor into a firing solution - the effect being able to produce a miss as close as 700m, in hand with inherent rifle accuracy, under typical circumstances if not accounted for.

Skill
FM/BS-411 - Manually calculate and adjust for Coriolis effect’s horizontal component
Skill
  • Calculate the horizontal deviation caused by the Coriolis effect using [the Horizontal Coriolis Force equation] or comparable methods
  • Integrate the calculated value into the final ballistics solution
Skill
FM/BS-412 - Manually calculate and adjust for inclination
Skill
  • Calculate the vertical deviation caused by the inclination between the firing position and the target value using [the Better-Improved Rifleman’s Rule equation] or comparable methods
  • Integrate the calculated value into the final ballistics solution
Guide
FM/BG-529 - Inclined Shooting: Introduction
Guide

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Guide
FM/BG-455 - Better-Improved Rifleman’s Rule equation
Guide

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Skill
FM/BS-414 - Manually account for spin drift
Skill
  • Use observed correlation and/or recorded data to estimate the horizontal deviation caused by spin drift, or calculate using an appropriate method
  • Integrate the calculated value into the final ballistics solution
Skill
FM/BS-415 - Manually account for the Eötvös effect, the vertical component of Coriolis
Skill
  • Use observed correlation and/or recorded data to estimate the vertical deviation caused by Eötvös, or calculate using an appropriate method
  • Integrate the calculated value into the final ballistics solution
Skill
FM/BS-416 - Manually account for changes in humidity, pressure and altitude
Skill
  • Use observed correlation and/or recorded data to estimate vertical deviation due to changes in humidity, pressure and altitude
  • Integrate the calculated value into the final ballistics solution

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