Originally Posted by matt_3479
Im not sure how the turrets actually work and i would like to know how the CDS and other turrets work?
with the CDS (Custom DIal System) you buy the scope and send Leuold the drop information for your rifle/bullet/atmosphere. They send you back an elevation knob marked to match your ammo based on the information you sent. http://www.leupold.com/_images/lightbox/cds_detail.jpg
CDS is not a rangefinder.
It does not assist in calculating windage.
It is not a drop calibrated reticle. You still have to turn the knobs. What it does do is eliminate having a lookup table to convert distance to drop... but only for one BC and one muzzle velocity and one air density (or at least ones that are close to the same).
OTHER RETICLE - KNOB systems:
Angle calibrated target knobs with simple crosshairs.
Good - works with any bullet/velocity/atmosphere.
Bad - no rangefinder - needs lookup table (or computer to determine drop and windage.
Requires knob twisting or any change in distance or windage.
Angle calibrated knobs with Mi-Dot or MOA reticle
Good- works with any bullet/velocity/atmosphere and as a low precision stadia rangefinder
Dots may also be used with limited precision for windage and elevation holdoffs.
Bad - still needs lookup table for drop and windage. Requires knob twisting for longer shots.
BDC reticles - with ballistic cam (ART scopes)
Good - Adjustable cams can match various ammo/velocity/ atmosphere. Built in low precision stadia rangefinder. Faster than target knobs. Most useful as a dedicated medium range scope on military rifles using only one ammo type.
Bad. Difficult to set for different bullets, velocities and atmospheres. Must have known target size to calculate range No help for calculating windage. Less precise than target knobs.
Drop claibrated reticle. -Springfield armory and others.
Good Very fast. No knob twiddling. Can range to known size targets or can work with a separate rangefinder. No knob twiddling with normal use.
Can also be used with clicks and lookup tables, but no advantage over Mil-Dot in that use.
Can help with windage by interpolation. Probably the fastest "stand alone" system.
Bad - Reticle matched to one bullet/velocity/atmosphere. Limited precision.
Adjustable calibrated reticle. Zeiss Rapid-Z
Similar to drop calibrated reticle, but also uses the scope's zoom feature to partially compensate for bullet velocity. It assumes moderately high BC bullets for the shape of the trajectory, but can adjust for a fair range of velocity. No knob twiddling for bullets within it's useful range. (most medium caliber high power rifles). Fast.
Bad. calibrations are compromises. as exact trajectories vary with BCs. Not for high precision shooting. Scope must be set to a specific magnification which depends on the ammo.
Angle calibrated grid. - Horus Vision
Good. Works with any bullet velocity, and atmosphere. The most precise elevation and windage method without twiddling knobs and counting clicks. Faster than target knobs.
It can be used as a stadia rangefinder but that is a waste of the scopes inherent accuracy. One benefit is that It makes zeroing the scope easy ( a featured shared by Shepherd dual reticle scopes).
Bad. A little less precise than a scope with good target knobs. A very busy reticle which requires good eyesight just to read the reticle when shooting at long range. Hard to use in low light. Requires lookup table or computer to determine settings (same as using target knobs).