I have a Leupold 4-12x with the LRD reticle. Reading the literature that came with the scope, I can approximate my load to some of the examples provided. The trouble is, the reticle is calibrated when the scope is on its highest magnification. I would like to have the option of shooting with the reticle at different magnifications that fit the situation. Has anybody found an easy way to calculate the differences?
thanks

Moe, the system is based on an inversely proportional equation. As magnification INCREASES, reticle subtension DECREASES, so at 6X the subtensions will be 2X that at 12X (assuming the power ring is calibrated relatively accurately). I always use my ballistic and rangefinding reticles at the scope's highest power regardless of subtension, but that's admittedly not the only way to do it. I just match the load to it, put the dope in the ocular cover of a Butler Ck. scope cap cover, and go hunting. I also use the plex post tips for windage reference (calc'd for 10 mph x-wind) as well-- they're excellent for that really. Your 4-12X plex post tips subtend 5.66 MOA, x-hair to PPT @ 12X. That's an excellent subtension for decent reticle windage reference. 1 entry on my range sticker may look like this--

450-2.9-0.8

...obviously range, elevation, and windage, no headers needed.

There is a very easy method to recalibrate the reticle to get the best trajectory fit tho (even hundred or 50 yd. intervals). Let me know i'f u're interested in that system, and i'll explain it.