there are many available online programs/ballistic calculators that take into account every detail of your gun/load and you can evaluate how high to sight in at 100 yds (or what velocity handloads are required) to be dead on at 300-800 yds using the diff crosshairs(and they work! you must chronograph your loads, know the bullet b.c., sight above bore height, elevation, temp., etc. etc. etc.-many variables- or have faith in the marketing claims on the factory ammo boxes

Many factory loads don't perform as advertised, and certainly not out of all guns.) Most ballistic plex reticles are set up perfectly (or nearly perfectly) for the most popular calibers (or ballistically similar.) But yes, after the above it must be field tested. Many BDC reticles come with a "tape" for various calibers to simply stick on the scope as a cheat-sheet (the mfrs have already evaluated the above. the shooter must simply conform his setup (assuming rifle is properly accurized, if need be) to the scope design. Burris is excellent in this department! This "tape" shows a typical 2" high 06 sight-in at 100 yds being dead on to 500 yds using their ballistic (BDC) reticle. It's good to about 850-950 using higher velocity (.257-.338) rounds and high b.c. bullets. Mark Bansner giggled at first when I put one of these scopes on one of his ultimate ovis guns (in my .264 WSM cartridge,) but no one was laughing when we were plugging sheep at 720 yards using same (or 4" wide woodchucks at 550 yds using same and .22-250.) Most guns fit into the 1", 1.5" or 2" high at 100 to be dead-on at 200, but some higher V guns work out to be 0.9 or 1.25" (for precision accuracy at 200 and beyond, per the scope design.) 30-30, 45-70 and 54 cal muzzleloaders-lol just use 1 crosshair or open sights and don't take long shots!!! lol
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