Hence my sighting at the MPBR with a 3" radius.
Hoyt, do you include the accuracy error in your calculations?
I usually do my initial calculations/comparisons using a 2" group for ease of math..
ie/ at 100yds, you add 1" to the upper limit, and at the lower limit, you add the negative.
for argument: at 250yds, I'd add a -2.5" to the lower limit
Therefore, if I can get my rifle to shoot better than 2" groups, I know my bullet will be within the MPBR zone.
without that, you could theoretically be outside your zone and have a miss and not know why.