Agreed the tables are nothing more then a guess the only true way is to verify at all distances you will expect to be shooting with your hunting load. As far is + or - and zero that is based on distance of shots, confidence level, etc. I personally like my PBR to stay roughly within a 6" tube, my particular rifle and load this usually means +2" @ 100which allows me to hold stead fast on game from 0 to 300 yards. After 300 yards i need to adjust the crosshairs verticallyas per what my range time has indicated to remain within the vitals of the animal. I used to go with a larger tube but it no longer fits my currentmodel for hunting with a CF (exceptionbeing pronghorn hunting where I error on the + side due to the average ranges being on the longer side of things).