Question on sighting

[paulenetedder]

I just finished sighting my rifle at 75 yards using a bench rest, the target board is around 4ft off the ground. I got like 1/16 of a inch grouping off of the bullseye which is the size of a dime. But when I started shooting some resettable plinkers which were on the ground at the same distance, I noticed I had to raise the crosshair up a bit to hit it ( I wasnt using the rest when shooting). What's the reason for this? and should I continue to adjust?

 

[GeneT]

I wouldn't adjust anything. The angular difference is pretty much inconsequential. (And if it were, you would be hitting high.) Whatever the problem, if you can go back to the bench and it shoots the same, it's not the rifle.

GsT

 

[Hunter]

The angular difference is pretty much inconsequential. (And if it were, you would be hitting high.)

Please explain that.

 

[GeneT]

Please explain that.

If you're shooting at a sharp elevation (up or down) you will hit higher than a zero obtained by firing horizontally. Your trajectory changes, because gravity is no longer acting perpendicular to the line of sight. So only a fraction of gravitational acceleration is moving the bullet in a direction perpendicular to the line of sight, resulting in a higher hit.

GsT