Originally Posted by GP Fan
The mcarbro trajectory chart has a 25 yard zero for all cases. From a 16" barrel (aka a PC Carbine) a 9 mm is 0.1" high at 10 yards and less than 3/4" low at 40 yards. Those rise and fall numbers are absolutely negligible in a typical home defense situation and there is no need to holdover or under unless your house is as big as a railway station.
I am familiar with the chart you are referencing but there is absolutely no way those numbers represent reality. First of all they call the numbers in the chart "drop" but it is actually a windage elevation chart for bullet trajectory. They are not the same.
For a rifle with an offset of 1.75" between the line of sight (LOS) and the bore axis, at contact range a sight picture would obviously result in a point of impact more than 1 1/2" low. The only way one could achieve a POI .01" above the line of sight at 10 yards would be to zero the sights for a very large angle of elevation of the bore to the line of sight, for example a "near zero" at 9 1/2 yards so that the trajectory would first be crossing the LOS just short of 10 yards.
With that type of zero with the typical 124 grain 9 mm Luger cartridge your true zero or far zero is going to be out somewhere around 120 yards where the bullet would cross the LOS the second time. Maximum ordinate for such a zero, cartridge, and sight height would be 5" above the LOS at around 66 yards.
With 115 grain ammo the far zero would be just about the same but the max ordinate rise above LOS would be slightly more.
If one accounts for the higher muzzle velocities one might expect from a 16" barrel, the same near zero and sight height would give the trajectory a bit higher arc. The true zero would now be out around 135 yards and the maximum ordinate would be about 6" above LOS at around 75 yards.
With a sight offset of 1.75" one will have to deal with some degree of holdover for a precise hit at very short ranges. One can reduce the holdover slightly by zeroing at a very short range, but then one will have to hold under (hold forward) by an even greater amount at plausible self-defense ranges beyond the near zero point.
If a PCC is to be used for self-defense I would suggest a zero somewhere in the 40-50 yard range. If one looks at the ballistics for Federal 124 grain HST for example, given a sight height of 1.75", standard atmospheric conditions, and bumping the expected muzzle velocity up by 100 fps to account for the longer barrel, a zero at 50 yards would result in a near zero at around 28 yards. From 20 yards all the way out to nearly 60 yards the trajectory would be quite flat, with a POI within one caliber (bullet width) of the LOS at all points. At 6 yards and at 70 yards one would have to deal with about 1.2" of holdover, which is quite manageable. POI at 100 yards would be just over 5" below LOS.
I would not consider a 9 mm pistol caliber carbine a reasonable choice for a self-defense firearm at a range of 200 yards, assuming that there would ever be a justifiable reason to shoot in self defense at that range. At 200 yards with a 50 yard zero you would be dealing with a POI below LOS of over 40 inches. Assuming you could adjust for this, the bullet would be dropping like a rock, so even a relatively small miscalculation in range would dramatically impact the POI. The projectile will have pretty low kinetic energy at that point, and very low momentum. A JHP round may well fail to expand.
Could you lob a 9 mm Luger projectile in at 200 yards known range and make a hole in paper? Sure.