Harrakhan, i've been studying this reticle ranging stuff for several years now, and the best system i've ever seen is sort of a combination of the TDS system, and the mil-ranging formula. TDS used his "ballistic reticle" as a ranging tool by using 1 of the stadia lines as the "main ranging unit", and then the others were calculated as simply a percentage of that main ranging subtension in inches, or cm., whatever measuring system u choose. To better ubnderstand it u have to begin thinking of the mil-ranging formula as really a "stadia-ranging formula" since the formula simply describes the relationship between stadia subtensions vs. target size vs. range. Here's a link to an article i have on the web, titled, "Tactical Ballistic and Ranging Reticle Analysis" that describes all my research to date. There r a few mistakes in the article that should be updated soon, but the concepts r sound. Refer to Item C) 1 + 2 Reticle Rangefinding-- www.ottllc.com/specialtypistols/sp20.pdf
Here's a copied portion of a Sniper's Hide discussion referring to the Nightforce NP1-RR reticle (the 1 with all the circles in it)--
As far as the reticle ranging goes it's set up for 9", and 18" targets @ the highest magnification. Looking at the website it shows the 1st circle is 9" in diameter @ 300 yds. That means the 100 yd. subtension should by 3", with the baseline to step measurement @ 2X that or 6". Now here's the fun part about reticle ranging-- the best system that' i've come up with is the "mil-ranging formula" that is really not milliradian specific-- it can be used for any stadia-stadia subtension out there (plex, ballistic reticle, custom reticles, AND NP 1-RR CIRCLES/STEPS). The 1000/36 factor in the mil-ranging formula is simply the dot-dot subtension in inches since the factor can be simplified to 100/3.6 (look familiar-- like maybe 3.6"/100yds?). Now simply calculate the other circle subtensions, and then punch them all into the mil-ranging formula to use the ranging system for any size target u want-- like this--
9" 400 yd. circle = 9/4 = 2.25" @ 100 yds.
500 = 9/5 = 1.8"
600 = 1.5
700 = 1.29
800 = 1.125
Now, just punch all these figures into the "modified mil-ranging formula" like this for say a 7.3" (Leupold Varmint Hunter reticle's std.-- if i remember right)pr. dog--
Circle 1) 7.3" x 100 yds./3" (300 yd. circle)/bracketing gap target fills in tenths of that total gap--1.0 =
7.3" x 100/3"/1.0= 245 yds. for the 3" bracketing gap "300 yd." circle.
Circle 2) = 7.3 x 100/2.25/1.0 = 325 yds.
Circle 3) = 7.3 x 100/1.8/1 = 400
4) = 730/1.5 = 490
5) = 730/1.29 = 570
6) = 730/1.125 = 650
This system is very flexible, and allows the use of just about any reticle subtension for any tgt. size-- INCLUDING THE BURRIS BALLISTIC MIL-DOT--either dots, or line stadia. Fact is, u could actually measure the reticle subtension @ any range and punch it into the equation.
Hope this helps some. Let me know if it doesn't-- this stuff can be quite confusing-- took me more than a year to figure it out.