BDC (Bullet Drop Compensation) locking turrets are the last evolution of the hunting BDC turrets on the market. Instead of numbers of clicks, these turrets have engraved the numbers or color dots for the corresponding distances. BDC turrets are meant for hunters for long-range hunting, since the only information needed is the distance to the target. If the shot must be made on 300 meters, the turret only must be dialed to 3, and bullet drop is compensated on this distance. The hunter does, however, have to take into account that wind drift is not accounted for when using such scope, and the best way to use BDC turret is when there is no or almost no wind.
Since every BDC turret can only fit to one ballistic curve, an exact calculation must be made to determine which BDC turret fits a specific ammunition. Because of wide variety of different ammunition and barrel lengths used, scopes with such turrets, usually, come with a set of different engraved rings, which have different spacings between distances, or they have adjustable marks for different distances. The majority of scope producers also offer specific ballistic software that helps user to determine which ring is the right one for its rifle and ammunition.
The locking mechanism on such BDC turrets helps to protect against unintentional dialing of clicks and accidental movement of the POI (point of impact) of the scope. The majority of these advanced BDC hunting turrets also have a Zero stop function that stops rotation of the turret below the zeroed distance.