| billyburl2 wrote:|
And because the scope is a second focal plane scope,and the reticle does not change in size with the change magnification, the mil-dots (which are usually .2 mils) will actually cover more of the target at lower powers.
That's exactly right. A scope where the reticle is located in the 2nd focal plane is also referred to as a non-magnifying reticle, so the apparent size of the reticle does not change with magnification. Therefore the subtension (the downrange measurement) does change. It's very close to being inversely proportional to magnification also at any given range. The optic can also be used for reticle-rangefinding using the 2.38 IPHY subtension more accurately than the std. mil-dot subtension of 3.6 IPHY, BTW.
That is the reason i bought a Nikon Buckmasters 6-18x mil-dot for a prairie dog rig i have. I specifically selected that mil-dot optic, since it is cald. for a power much lower than the highest (12), but at 18x the dot's become 0.48 inch per hundred yds. (66% of 3.6, since 12 is 66% of 18), or basically a 1/2" dot compared to ~3/4ths (.2 mil.). The dot to dot spacing also decreases by 66% of 3.6 or 2.38 IPHY.
It's amazing the misinformation that's out there. That link to the mil-dot site noted above is a respected website link, but their saying that the dot to dot subtension is designed to be interpolated into tenths using a 0.25 mil. dot diameter. They're talking about the old USMC M-D which is designed to be broken down into eighths (0.125 factor) interpolatively, not tenths.
I would check with the company since the mil-dot dot subtensions are not commonly advertised for many optics companies. Most use 0.2 mil, but i have seen 0.22 (Sightron) and 0.25 (some older Leupolds).
Edited by sscoyote - January/16/2010 at 17:58