A milliradian is an SI derived unit for angular measurement which is defined as a thousandth of a radian (0.001 radian). Milliradians are used in adjustment of firearm sights by adjusting the angle of the sight compared to the barrel. Milliradians are also used for comparing shot groupings, or to compare the difficulty of hitting different sized shooting targets at different distances. When using a scope with both mrad adjustment and a reticle with mrad markings, the shooter can use the reticle as a ruler to count the number of mrads a shot was off-target, which directly translates to the sight adjustment needed to hit the target with a follow-up shot. Optics with mrad markings in the reticle can also be used to make a range estimation of a known size target, or vice versa, to determine a target size if the distance is known, a practice called "milling".
The PSO-1 reticle in a Dragunov sniper rifle has markings with 1-mrad spacing, which can be used to compensate for wind drift, impact correction or range estimation.
The Palais de Rumine, one of the former buildings of the University of Lausanne.
Mildot chart as used by snipers.
Estimating range using the hands on an extended arm as a reference for the angular size in mrad.
In shooting sports, a shot grouping, or simply group, is the collective pattern of projectile impacts on a target from multiple consecutive shots taken in one shooting session. The tightness of the grouping is a measure of the precision of a weapon, and a measure of the shooter's consistency and skill. On the other hand, the grouping displacement is a measure of accuracy.
Handgun and paper target showing grouping of ten shots
A grouping made with a five-shot revolver
Eight-shot grouping
Multiple shots from a semi-automatic handgun
