Thought i'd copy this over from the Long-Range thread on Specialty Pistols: Been looking a lot at the TDS Tri-Factor System lately in the Swarovski/Kahles scopes. The system he uses for ranging can be modified to work for any ballistic reticle, such as the LR handgun Ball. Plex. Here's how it would work: Ball. Plex reticle subtensions for 3-12= 1.4", 4.1, 6.8, 10.1 Now using the entire 10.1" gap for a 24" back to brisket cow elk, then the modified mil-ranging formula is: 24" x 100/10.1/# stadia units in tenths of a unit that the 24" target brackets, or: 1 stadia unit= 240 yds. .9 SU = 265 .8 SU = 300 .7 SU = 340 .6 SU = 400 .5 SU = 475 .4 SU = 600 Now each stadia line in the reticle can be used as a reference to have a more accurate system, helping a lot with interpolation, and to calculate what part of the gap each stadia is, just divide the full gap subtension into each stadia subtension as follows: 1.4/10.1= .1 of the total 10.1" gap, and 4.1/10.1= .4 6.8/10.1= .7 Now u have 2 more ranging references with the 2nd and 3rd stadia to help with interpolation (the 1st stadia-- .1 calculates to 2376 yds.-- a little too far for my guns, i think). This system has been proven by the originator of the TDS reticle to work quite well for ranging purposes for larger game (deer and bigger).