goodgroup: "Whoa. I disagree. For long range shooting or hunting, an ES of 50 would not be acceptable to me. You would be asking for big time vertical dispersion at distance!"
No argument on the value of an ES of 2 or less but as a percentage of the speed, 50 isn't bad. That varation, taken alone, won't prevent many hits at any range, IMHO.
Consider a 7 Mag shooting a .534 Hornady SPBT at a specific speed ( ie, not an average) of 3,100 fps and zeroed at 500 yards. That's a pretty fair long range load. Hornady's #4 book of charts says it will drop 17.1" at 600 yards. Then, at 3,000 fps (100 fps slower) the same bullet expects to drop 18.4" at 600 yards, a full 1.3" difference.
An ES of half that velocity difference (50 fps) would only cut the drop to something like 7/8"? If even that estimation is off by a half inch, it's certainly not enough to cause a miss on a 600 yd. p' dog! And all that calculating assumes zero wind and mirage to make aiming harder and assumes each bullet is cutting one hole groups out to infinity, none of which is likely in my world!
I think an accurate, reliable load with an ES of 50, varying only 25 fps from the middle speed, is a pretty good load in the real world.
Not perfect, but pretty good.