I have an older S&B 2.5-10 x 50 with an A8 reticle on a weatherby 270mag and I never really used it for range estimation but now I would like to learn how and what power I should use for ranging.

Yessir--looks like that's a plex-style reticle which is what i used for an example in this video of how to rangefind with any multi-stadia reticle system you may be using-- http://www.longrangehunting.com/forums/f94/reticle-rangefinding-math-youtube-87994/

thanks for the reply. this is a FFP 2.5-10x56 that ive had for 20 years and I still like the clear glass and although I own 4 nightforce and they have the 2R which is a lot easier to use.

No problem using a plex reticle for rangefinding. In fact if the subtension is smaller than the milliradian, it will probably also be more accurately applied. Just remember to use it just like a 2-unit "mil-dot", i.e. 2 plex post tip to x-hair units. It'll be a bit more accurately applied this way than using it like a 1-unit mil-dot from plex post tip to plex post tip. Don't expect "stadiametric rangefinding" to be accurately applied on game animals that vary in size a lot though--deer, elk, etc. Just today whilst hunting coyotes i had the opportunity to reticle-range a doe antelope at a guessed 14" back to brisket using the Burris Ballistic Plex reticle. I guessed .8 of the 1st to 2nd lines down (3.0 inch per hundred yds.) from the sitting position--not seaddy enough really for the most accurate "mil-reading". It lasered at 625 yds. Here's the equation-- 14 x100 / 3.0 / .8 = 583 yds.--NOT CLOSE ENOUGH! I have found stadiametric rangefinding accurate on most game spp to ~500 yds. max. Stadiametric Rangefinding is the best application of the SWAG acronym i've ever seen really.

thanks for the info and reply .your post reminds me that I have MUCH more to learn about using my standard scopes for ranging. some or the terms you used I have never heard before and gives me a lot of new useful info to study and try to put to use

Good lucka nd have fun with it--although it's not a perfect system, it's certainly better than guessing. I have already had feedback from 2 different guys who used it to range coyotes between 400-500 yds. and it worked for them. FYI, there are 2 important aspects to remember about reticle [and turret] applications, and that is-- 1) Reticle subtension is ~inversely proportional to magnification [in 2FP optics], and 2) The mil-dot mil-ranging formula actually defines the math behind any multi-stadia reticle and turret rangefinding and downrange zeroing applications.