BGF - in a round-about way, you've said exactly the same thing as cal. 45's brother, and mine, and Shovelbuck, except your first statement is incorrect, then clarified with the next. This might cause confusion. The ball starts to drop the instant it leaves the muzzle.
My .32, .40, .45, .58's & .69 all show this sighting phenominum - sighted at 25 yards, they are also just about dead on at 50 yards, give or take 1/2".
Taylor's explanation is direct, enough information and most importantly, to the point. The point blank is the actual range at which one can take aim at an object or animal and be gauranteed a perfect hit, without having to aim high or low.
This was the only error on his post- minor at that. The point blank range depends on the allowable error- ie: how high or low can the ball be before being ineffective on the intended target? If it is allowed 3" high above the line of sight (sights) and 3" low, on a large deer for instance with a centre hold with hunting loads, most round ball guns will have about at 135 to 140 yard point blank range. that is, the bal will never be more than 3" above nor below the line of sight. To have this long a point blank range, it must be sighted properly initially - probably in this instance, at about 110 or 115 yards, maybe 118yards, testing is necessary to show this - it is not written in a book. Sight them to close, or too far away and the point blank range becomes shorter, generally, due to not allwoing the necessary rise, or introducing excessive rise between the muzzle and the sight-in range if sighted too far, say 125 yards or 130 yards, making the ball miss high at closer ranges.
Computer programs are useful in helping initial settings, but actual shooting is necessary. My self and for hunting I prefer to have no more than a 100yard zero, then find what maximum range gives me the point blank range- ie: a drop of 3" to 4". If group size is so large as to not show this fine a separation in range, you are testing beyond your accuracy range. imho.
As Taylor indicated, sight height does make a difference and also causes more height with increased loads and/or patch changes. The lower the sights, the less change occurs with increases in powder charge - somthing else to think about. Too, higher sights can work to your advantage ie: if you normally use squib loads for plinking, say 70gr. 3F or 80gr. 2F in a .50 or .54 and thus giving a zero at 50 yards (and 25),increasing that load to 100 3F to 120 2F (or whatever) for hunting, might make the ball travel to 2 1/2"high at 50, 3" high at 65 yards, thus giving you a perfect point blank as noted above, and having an actual zero of about 100 to 110yards. Hypothetical example only - guess what - YUP - you actually have to get out and shoot it to find out. See what fun this is?
