Other assumptions in that method are the accuracy of the BC value and the line of sight above bore height.
Heck even worse than those is the assumption that the 100 yd zero is really zeroed. Seems to me most of the guys doing stuff like this are shooting 3 shots at best (and sometimes just one) to "zero", not wanting to consider how randomly distributed those impacts may be, or how much that affects the results down range.
Mathman did bring up some valid points but it also brings up the fact that if you used the ballistic charts in the Hornady and Nosler books from the 80’s and 90’s that these manufacturers didn’t know sh*t about what their BC was nor the line of sight above the bore for deriving said charts was all a bunch of horsesh*t. To which I may tend to agree at times which is why I always confirm drops even with a known velocity and when using Sierra infinity drop calculation.
Now the real assumption that is a bunch of Sh*t is that I don’t know how or when my rifle is zeroed and that I make that determination on just 3 shot groups or just a plain 3 shots and call it good. Unless you have been to the range and witnessed my zeroing you haven’t got a clue which you don’t since I know for a fact you have never been there.
