How Maximum Point Blank Range (MPBR) misses the target:
"Man's got to know his limitations". - Inspector Harry CallaghanHere we have a 6" target representing the "Vital Zone":
If the bullet goes thru the exact center of a paper target at the zero range, it will scrape the edge of the 6" target at MBPR. "You are guaranteed a hit on the Vital Zone out to MPBR".
But how many of your shots hit the exact center of the target? You shoot groups. Assume you shoot 6" groups in the field at MPBR. Half your shots will go low and score as misses at MBPR. About halfway, half your shots go high and miss.
You've got to ask yourself a question: 'Do I feel lucky?
The statement "You are guaranteed a hit on the Vital Zone out to MPBR" is false, but it gets repeated mindlessly by the people who encourage hunters to zero at ranges beyond their capabilities. Plus you have to know if the range is greater or less than MPBR, which still requires range estimation skill.
If you actually want to hit the target every time without making adjustment for range, you will have to zero at a shorter range than MPBR. As a rough guide, calculate MPBR, subtract half your group size at that range from the size of the target. Use that reduced target size to calculate MPBR again. This will keep you on target at the maximum range, you will still be a little off at the halfway point, but it will be an improvement.
The free program you can download here calculates MPBR taking group size into consideration at all ranges for a more accurate result.
The other method is to know what your bullet drop is at different ranges, and adjust your point of aim. If you zero at 150 yards, you might remember the drop for 200, 250, and 300 yards for example.
Free Ballistic Simulator Software updated Sunday August 01 2010 at 11:43am. Email Frank Clarke About Frank Clarke