Re: Rangefinder for actual horizontal distance
For several reasons that are long and hard to explain, shooting for the actual "horizontal" distance is not the best choice. At closer ranges it works fair. The further the shot and/or the steeper the incline, the more error you will have.
A MUCH better method is to take your bullet drop in either inches, MOA or MILS and multiply by the cosine of the angle. Use that value as a correction. This is called the advanced rifleman method.
The absolute most accurate method is neither but it is a long lengthy proccess to do the math. For most real world hunting situations, the advanced riflemans method is a fairly accurate solution unless you are talking about small varmints.
Advanced riflemans method example:
675 yards, 25 degree slope, bullet drop for 675 yards is 91.75 inches, cosine of 25 degrees is 0.906. Take 91.75 * 0.906 = 83.125"
The reality is though that to do the formula correctly you would find that the actual bullet drop is 80.5" and not 83.125". However, 2.675" off is not too bad for a deer size target when aiming for the lungs.
To shoot for the horizontal range you would be shooting for 611 yards. The bullet drop with my example load at 611 yards is roughly 72". That is roughly a 10" margin of error. A 10" error is too much for a clean shot. The best policy? DONT shoot for the horizontal range.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
Last edited by Michael Eichele; 01-15-2011 at 09:58 PM.