An 8 year old post resuscitated. Outstanding. The topic itself however seems to be quite prevalent on various pistol forums......."my pistol shoots low at 3-10 yards". That is true. However the understanding for the observation often times seems to be mystical.
The modern factory sights of the full size standard Sig pistols , e.g. P226 are set up to have point of aim = point of impact @ 25 meters.
The Sig P226 with a 6.3” radius, sighted in at 25 meters, the bullet trajectory has to climb ~ 11” above the muzzle height in order that point of aim = point of impact @ 25 meters. The old Sig adage "float the dot, shoot the shot".
Anytime you desire a POI at a distance closer than your gun sights are zeroed at, you will have to use a POA that is higher at that closer target. The extent that you have to hold high will depend on your cartridge ballistics, sight radius length and distance to target. The Sig's @ 7-10 meters POI will be ~ 2/3 low of the factory sight zeroing; 10/25 x 11 “ = 4” of climb has occurred.
Remember:
Any deflection of the sight line during trigger manipulation will have the same magnitude of effect on POI as your sights being misaligned by an equivalent magnitude.
For the P226 every 0.007" deflection of sight picture (thickness of common index card) the result is a change of 1" in point of impact. That means if you disturb the sights 0.1" it results in a 14" miss @ 25 yards or 3/4 the width of average male torso.
The fixed sight-bore axis angle differential determines the vertical launch angle of the bullet; the launch angle can be adjusted by changing sight heights .
It must be understood that the instant the bullet leaves the muzzle it is moving downrange and UPWARD AT A DETERMINED VELOCITY!
In the case of the P226 the angle is~ 0.69 degrees which imparts a vertical velocity to the bullet the instant it leaves the muzzle. As a first order approximation, for a muzzle velocity of 1140 fps, this angle imparts a vertical velocity of 13.7 fps at the muzzle; time for the bullet to traverse 25 yards (75 feet) is 0.066 sec, at which time the bullet has risen 0.066 sec x 13.7 fps = 0.9 feet (10.8”)……there is your 11” at 25 meters; the downward force of gravity is not considered here, however can be used to precisely determine at what time in the flight path the bullet will reach its apex (vertical velocity = zero). It is easy to see how just muzzle velocity alone will impact vertical impact on the target.
Importantly, it is important to understand the one can change their front-sight ratios all day long but IF one is shooting at a target INSIDE the distance that the sights are zeroed at they point of impact will always be low!......unless one cock's their wrist into some goofy convolution.
