The Leatherwood ART (Automatic Ranging Telescope) off the M21 Sniper Weapon System; is the concept of a scope that automatically adjusts elevation as you change magnification a technological dead end?
These scopes seem like such a practical idea to me. If you know the size of your target, you adjust your magnification until the unchanging (second focal plane) scale on your reticle matches the size of your target. So you adjust magnification until the 18" ruler on the reticle lines up with your 18" wide target. As you do this, the scope automatically adjusts elevation, according to a mechanical cam profiled to match the ballistics of the gun and ammo you're using. Then you worry about wind dope, and pull the trigger.
From what I read these scopes were designed and made by Mr Leatherwood and issued by the US military in Vietnam, and apparently weren't that well received due to durability problems.
But the underlying theory seems sound. The alternatives involves ranging with a reticle or other method, then remembering what your bullet drop at that range is, and then dialing elevation manually or compensating for your drop on a complicated reticle. The Leatherwood ART system makes the process simpler and remembers elevation dope for you, and the mechanical "cam-puter" could be disengaged to revert back to standard scope adjustments.
As far as I can tell the only company using this technology today is a company called Hi-Lux, which I gather is using it on Chinese-made scopes that don't have the best reputation.
Has this technology ever been used elsewhere?
Seems like there'd be more of a market for a high quality version of this product, with custom-ground cams to ballistically match whatever somebody was shooting.
Here are a couple of Hi-Lux's videos showing off their contemporary version of this scope, and showing how to shoot with it: