Zoogster, read freakshow10mm's post. That is the true definition for Maximum Point Blank Range. And anything from 0 to MPBR would be point blank range.
Yes I oversimplified.
What a said would have simply gave a bore diameter maximum point blank range.
He gave a 10 inch diameter target point blank range, or 5 inches of drop from the center.
Neither is really suitable for civilian applications of firearms IMHO, and most references to the term for self defense and hunting with handguns (which generaly have much greater bullet drop than faster rifle calibers) are using a
three inch drop reference.
It is not the military and simply hitting a torso is not acceptable. Most vitals are only a few inches in diameter and so a point blank range of a few inches is more realistic for hunting and self defense conversation.
Many people here claim amazing accuracy at the range, so you would assume thier point blank range diameter would be small enough to enable the benefits of thier abilities. If you are constantly drilling out the 1" bullseye of your targets, then a smaller point blank range is probably appropriate rather than a 5" drop as 10mmfreakshow gives or the standard 3" used by most catalogs in computing maximum point blank range on on a firearm and cartridge.
The reason thinking of it the way he describes is bad for others to learn as the definition is because you could make anything visible on the horizon "point blank range" by simply putting the firing platform at high elevation and determining the point blank range to a very large target at the same altitude (instead of 10 inches like his example, let's say hundreds of feet.) That would still technicaly be "point blank range" of hundreds of feet with hundreds of feet of bullet drop, distorted beyond any realistic usage of the term.
Since firearms are often expected to perform within 1-4 MOA and most regulation targets have a bullseye around 1" in height which many consistantly hit, point blank range means something different.
Simply hitting a torso size area is not acceptable, simply hitting a torso in hunting is inhumane, simply hitting a torso size area on a target with a 1" bullseye is unacceptable, so a 10 inch diameter is an unacceptable reference definition for most civilian applications.
Now if talking about artillery with a shell that has a blast radius of 50 yards, you have a very different point blank range requirement, and will as a result have a very different definition of "point blank range" when referenced casualy without reference to the exact diameter being described.
So I felt the boresight explanation was simple enough as it leaves firearms sighted beyond thier point blank range out of the equation and helps those unused to the term better picture what is being referenced. But clearly it was not a good reference.
The most important factor to clarify would clearly be what diameter the maximum point blank range being referenced is.
The largest factor in determining maximum point blank range is ususaly velocity due to the action of gravity. Projectiles in the air longer will be effected more by gravity. Of course drag, air density and other things factor in. Very fast rounds ususaly have a more distant point blank range.
Yet a round with a greater point blank range can end up having more bullet drop beyond the point blank range referenced, or within the useful range of the cartridge than a round with a better ballistic coefficient. So thinking of it as bullet drop is also not a good way to learn the definition. Further away a bigger but slower round can drop less than an initialy fast light round that normaly is defined with a more distant point blank range.
As a result it would even be possible to take two different cartridges and have one or the other with a greater "point blank range" simply be redefining the point blank range diameter of reference.
One may have a greater point blank range in a 6" diameter, and another in a 10" diameter where a greater ballistic coefficient has given it the edge.
So even just saying one round has a greater point blank range than the other is not always accurate without defining the maximum point blank range diameter being referenced.