Also shoot an OPTISAN Viper in 4x16 ... choose that over 4x12 for a couple reasons ...1st being not out at the end of mag range where some scopes may have clarity issues, backed down some from 16x to 12x makes sure image is crisp & sharp.2nd being 12x is not always exactly 12x on many scopes ... so by having a tad more Mag it is far easier to trust and make up dope sheets / bracketing charts.At 100 feet at 12x a RULER when viewed will scale at 1 dot per inch.Fine tune Magnification to achieve this calibrates scope very precisely for all ranging based on 12x values Scott