BDC stands for Bullet Drop Compensation, and BDC turrets offer the easiest way to dial number of clicks to compensate for bullet drop when shooting at longer distances. These turrets are usually found on hunting scopes for long-range hunting. These turrets are very similar to Tactical turrets; however, the main difference is they don’t have numbers for clicks engraved on them, but only numbers for the corresponding distances. On such turrets, 1 stands for 100m, 2 for 200m, 3 for 300m, and similar. Color dots, instead of numbers, are also very common; however, in such cases, the hunter must memorize which color corresponds to a given distance to the target.
BDC turret can only match one ballistic trajectory, and BDC turrets are always suitable for use with only one ammunition. When a shooter changes the ammunition in his rifle, the BDC turret must be changed to correspond to a new ballistic curve.
The best modern BDC turrets also have additional function of a Zero Stop (the turret doesn’t rotate under zeroing distance of the rifle) and locking mechanism.