Heat

Some information that I've learned on the first and second focal plane.

In a fixed power scope this would be irrelevant but in variable power scopes it can be important.

First focal plane reticles are installed in the optical path at a place forward of the ocular lense group. Second focal plane reticles are installed in the zoom mechanism of the ocular. It is said that there is essentially no point of impact change in a first focal plane scope as you change magnification. There can be changes in a second plane scope as the zoom is mechanical and physically moves the reticle. I am guessing here that you get what you pay for in the high end scopes and the shift, if any, would be extremely little to none.

First focal plane reticles remain the same size relative to the scope while second focal plane reticles remain the same size relative to the target. Thinking logically, it appears for a ballistic reticle that is based on MOA, that it would be better for it to be second focal plane as the reticle would change size at the same ratio as the target. In my limited experience with the B&C reticle in the Leupold line (first focal plane) the scope needs to be set at a particular magnification for the reticle to be of any use. I would assume the setting is actually relative to the particular ballistics of an individual cartridge/rifle combination. This magnification setting is usually near the upper end which could make it less then desireable if it is a high power scope at a more limited range of say 300 yards. I don't believe it would be of issue for an elk size target at 300 yards with a 3.5-10 magnification scope however. Understand that any ballistic compensation system will be affected by atmospherics, altitude, etc.

Ken....