Spin Drift: Calculation

Equation To manually estimate calculate spin drift, we only need to know the distance of our shot and how long our bullet will be in flight. ((SG * Time of Flight ^ 1.83) / Distance) * 1000 = Spin Drift in MRADs The variable “SG” is the stability factor of our projectile, considering many details of rifle and bullet construction. This information will be provided for commonly used rifle and bullet combinations in a chart below. Data Collection Time of flight can be found in the ATragMX under the “RC” button in the top right of the screen or derived in an online ballistics program. As the ATragMX suite is not available in situations where manual ballistics are relevant, time of flight information should be recorded prior to operation start. SG or Stability Factor is provided below for common combinations of rifles and projectiles for campaigns that utilize manual ballistics. Note that the following SG values have been further modified to simplify the initial equation: Rifle Twist Direction Projectile Modified SG M24 SWS Right M118LR .0759 M24 SWS Right M62 Tracer pending M24 SWS Right M993 AP pending Calculation Example Sgt McShooty is deployed as a Spotter (Manual) on a Honeybadger. He ranges a priority target at 900m, a shot that will have a time of flight of 1.8s. His sniper is using M118LR ammunition for this shot. ((.0759 * 1.8 ^ 1.83) / 900) * 1000 = .25 MRADs Because the rifiling of the M24 SWS barrel twists to the right, the bullet will deflect .25 MRADs to the right due to spin drift. Equation Limitations This equation serves tremendously in almost all circumstances, with very little inherent error included in the calculations, even within extended operating ranges. It should be noted that the "Modified SG" values provided do include atmospherics as a part of the calculations as air resistance does affect spin drift deflection over distance. When these provided values were assembled, default Arma 3 values of 15°C & 1013 milibars of pressure were assumed. Only when operations require the effects of a single shot to be guaranteed, and when atmospheric conditions deviate from default values significantly, a new modified SG value should be assembled. If the effects of a shot must be guaranteed and atmospherics vary greatly from default values, a new modified SG value should be assembled.