Castle Rock,
6.5BR is correct--I used the scope's plex reticle for shooting to 500.
I started using the system back in the 1980's, long before we had laser range-finders and so many scopes with field-adjustable elevation turrets. Of course, shooters had been using multi-point reticles before longer-range shooting for decades, but for some reason they never had a big following among hunters. Instead most hunters used plains crosshairs and "guesstimated" range, a really inaccurate method.
But when plex-type reticles showed up, it occurred to a few hunters that they could be very handy in both estimating range, by comparing the "gap" in the reticle to animals of known size, and by using the gap for longer-range aiming. In the 80's I was doing a lot of longer-range shooting, especially on varmints, and also guiding pronghorn hunters, where actually knowing the approximate range rather than guesstimating it helped a lot--both for informing my clients of where to hold, and in having to finish off wounded antelope myself, which happened occasionally.
Using a plex reticle for both purposes works very well out to 450 yards even with relatively "slow" cartridges, but does OK even a little farther with some rounds. The farthest I ever finished off a wounded antelope was around 550 yards, and while it took two shots I had a good idea of where to hold and didn't miss the first shot by much. Killed several of my own animals over the years out to 500 with the first shot, using a plex reticle both to estimate range and for the hold.
Of course, an LRF and turret-scope are more accurate, especially beyond 450-500, but I still like to play around with all methods, partly because of readers.
