Posted by JimM on July 19, 2000 at 17:31:54:
If a pistol's sights are zeroed for 10m, what will happen to impact point when shooting at 5m? Gravity would seem to dictate a higher impact point but I'm not sure about sight/target geometry. I've recently started shooting at 5m with a scaled target and all my shots seem to be going low.
Posted by geo. anderson on July 19, 2000 at 19:15:24:
:... all my shots seem to be going low.
Rememember, the pellet is starting off lower than the sights. Without digging into any exterior ballistics info, I'd guess that it is rising all the way to the 10M target and beyond, finally to begin to drop as the integrated acceleration of gravity equals and then begins to overcome the effect of the upwards launch angle.
For a .22 pistol with a dot sight (an inch or more between the sight axis and the bore axis), the zero at 50' and 50 yards is about the same, but the pistol will shoot high at 25 yards.
Posted by Rod Madsen on July 20, 2000 at 09:25:13:
This is an interesting geometry problem.
To simplify the numbers assume that the barrel is 1" below the sight, the point of hold you are using is 5" below the center of the target, and the distance from the end of the barrel to the target is 30'. Also assume that the path of the pellet is flat, we are having a match in space.
This means that the pellet must rise 6" above the sight line after it leaves the barrel, or 1" every 5' before it reaches the target. That means that the pellet will cross the sight line 5' from the end of the barrel having 25' to climb the remaining 5". At 5m, about 16' 6" from the firing line the pellet will be about 1.7' above the sight line (16' 6" - 8' = 8.5', 8.5'/(1"/5') ~= 1.7"). But the hold would be 1/2 5" or 2.5" below the center of the target. Thus the group would be 0.8 inches low, a low 8 ring.
My experience with Bulls eye is that using a center hold and the effect of gravity I really didn't have to make any sight changes from 50', 25 yd.. and 50 yd.
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