The last rifle I owned with a scope (it was a long time ago) had 3X9. I'm coming back to the sport and technology has galloped ahead. I was aware there are range finders, although I understood them to be a separate piece of equipment. They can give very accurate readings of the distance from shooter to target. Lasers as well as radio transmitters and detectors can provide that technology.

Someone recently told me that there are now available, scopes that have range finding capabilities integrated. What he described to me was an optical system that could identify the range and allow the correction to be made to produce a hit at the scopes point of aim. I think I'm describing it correctly. I'm guessing that it would produce the same result as if a range finder identified say, 352 yards to the target, and by knowing the trajectory of your rifle cartridge, and at what distance it is zeroed, you could aim over accordingly.

If an integrated range finding scope exists, how would it work? Would it not require calibration to a particular rifle, cartridge and zero point to calculate the correction?

Most of the Leupold variable power scopes have a built in range finding feature. It won't give you a precise reading like 352 yards, but it will give you a rough guesstimate for the distance.

With the Leupolds with the duplex reticle (where the heavy part of the posts taper to a fine line near the central crosshair), you need to identify some object downrange that is about 16" long (or tall). An example would be the length of a coyote's body, or the height of a deer's chest, etc. Next you place the point where the post tapers from heavy to fine on one side of that object and the central crosshair on the other side, and turn the power ring until that object completely fills the space. Then you read off the distance (200, 300, 400, 500 yards, etc.) from the power ring.

The Leupolds with the Boone & Crocket reticles also have hold over points for various distances. Some of the Springfield Armory scopes have similiar features as well. Other manufacturers like Sheppard have some scopes with range finding feature too I think. They're not exact, but they're better that just a guess.