Point of Aim and Point of Impact


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ForeignDude
April 14, 2008, 05:05 PM
Quick query, folks:

A pistol is sighted for center impact at 25 yds -- front sight over "X".

If I shoot it at 10 yds. with the front sight over the "X", should I expect the bullet to impact slightly above or below the "X"?

Ignore shooter factors, wind, and so forth...

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.cheese.
April 14, 2008, 05:10 PM
slightly above. However, with a pistol, and at short range like that (especially with only a 15 yard difference between what you've set the sights for and your target), the difference will be negligible. Gravity and the friction from the air will not have had enough time or distance to do much.

so I emphasize the word "slightly"

robmkivseries70
April 14, 2008, 06:26 PM
Hey Dude,
I am going to say you really can't tell with out knowing the heights of the sights above the barrel, and the velocity of the round. It would seem that the slower the velocity of the bullet, the greater the slope of the parabolic curve; thus, the two points where the round will cross the line of sight would be closer together. Whether this is possible on a 25 yard range is up for grabs. In a functional sense, a heavier projectile may leave the barrel when the piece is at a higher angle due to recoil and thus hit higher on the target. The best solution is for each individual to see how their POA and POI interact with their piece and loads at various ranges. I personally have seen rather large differences between 230 gr. ball and 200 gr. JHP in .45 ACP at distances under 25 yards due to the effects of recoil. This is the real explanation to the statement," Beware the man who shoots one gun." ;) (roughly paraphrased)
Best,
Rob

AndyC
April 14, 2008, 07:05 PM
Technically, it depends - as mentioned above, there are two points on the parabola where the POI and POA coincide, so it depends if it's sighted-in for the closer or further one - the latter being (99%) most typical. The reason for the parabola is because the barrel is underneath the sights - and if both were perfectly parallel, POI would never concide with POA.

However, technicalities aside, the bullet will initially strike lower than POA at a close range, cross the first POI/POA dead on, strike higher at the peak and drop down again to strike the 2nd POI/POA - so I imagine in your scenario that the bullet will strike slightly higher at a closer range (assuming your target is not closer than the first POI/POA).

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