Point of Aim/Point of Impact
Once you have sighted your rifle in at a known distance, you have achieved point of aim/point of impact.Point of aim is using the reticle crosshairs as your aiming point, point of impact is where the round will strike your target. If you have sighted your rifle in at 100 yards, your point of aim at 100 yards will be the point of impact of the bullet. Knowing how your rifle cartridge behaves in regards to ballistic trajectory now becomes a factor if you need to shoot closer than 100 yards or farther away.
By adjusting our aim point without manipulating your scopes windage/elevation knobs, you are using ‘Kentucky windage’ to adjust. If your rifle/scope combination is sighted in for a different distance, this information will change. There are applications for smart phones and computer programs available to assist you with that endeavor if you decide to use a different point of aim/point of impact.
Let’s say that you want to adjust your scope by using the windage/elevation knobs instead of using Kentucky windage to correct for bullet drop at the range of 400 yards. By manipulating your scopes elevation knob using the example of scope ‘A’ from above, each ‘click’ will raise the impact point up 1 inch (¼ inch at 100 yard, 1/2 inch at 200 yards, 3/4 inch at 300 yards and 1 inch at 400 yards). So to raise the point of aim to reflect the point of impact, you would have to apply 24 ‘clicks’ to your scopes up elevation. Be sure to know which way is the ‘up’ adjustment for your scope. If your scope has a mark with an ‘UP’ arrow, that’s the direction to turn the knob to raise the bullet impact up. Don’t laugh, I see a lot of people over think this operation. Just follow the marking on your scope to do what you want to have it do.
Most hunters use a cheat sheet with the ballistic information for the round they are using taped to the inside of the scopes dust cover. When the dust cover is open the ballistic information is printed on the cheat sheet for easy access. Range estimation is vital as well as knowing the size of your target.
Windage is more difficult to adjust for. At close range, a mild wind will not affect the impact of the bullet substantially. As range increases, the effects of wind increase due to the rounds loss of velocity. The only true way to learn your cartridges’ windage adjustment is to fire at distance on windy days, or doing research on the topic.
Leading the target is another use for Kentucky windage. If your deer is walking slowly across your field of view, you aim slightly ahead of the deer. The farther the distance, the farther ahead you have to aim. Usually, the deer will not be walking so fast that you need to adjust your aim point for movement. Do realize that the longer the distance from you, the longer the round will take to reach its target. Leading the target really should only fact in when you are shooting at a running animal.
I hope this series has helped to increase your knowledge of scopes and will help you to be better informed when making a scope purchase. If you have any questions regarding this article or about scopes in general or need help making your next scope purchase, please feel free to contact us at firstname.lastname@example.org.