Without getting into the nerdery, 1.6 times your Mean radius gives you the radius of a circle you can expect 86% of your shots to fall within.

So for ease of math. Say a rifle shoots with a Mean radius of 1 inch and you did that at 100 yards

Multiply by 1.6 and you have 86PH. The 86% probability of hit assuming a normal distribution. That number will be in inches at a certain distance.

In this example the 86ph is 1.6

Convert the inches at the distance to MOA. 1.047x1.6= 1.68 moa

Say you assume an 8 inch vital circle. So 4 inch radius.

Your Max range with an 86ph is 239 yards.

I built a spreadsheet to calculate all this crap.