Shifting Point of Impact?
Sun of a Gun!
As much as we love the sun – it can wreak havoc on our gun sights.
I noticed it around 40 years ago. While shooting under certain conditions, my groups appeared to move for some odd reason, even though my sight alignment seemed perfect. It wasn’t until I asked an old salty PPC shooter in our department that it was explained to me. This guy could shoot, and I’d seen him perform a ritual new to me every time he shot.
He had a carbide lamp and would blacken his front sight from the soot it produced. He explained to me how the range was built backward. The targets were positioned so the shooter was facing south.
Carbide lamp soot makes front sights blacker than black!
Blasted Sun
Early in the morning, the sun rises in the east and works its way across the sky towards the west. From the shooter’s position, at our our range, the sun moved from left to right as it got higher in the sky. During early morning hours, the sun caused a fireball of glare on the left side of the front sight. This glare gave the illusion that the front sight was thinner, prompting the shooter to unconsciously adjust their sight alignment. Sun glare disrupts your visual perception of the front sight, making your point of impact move toward the same direction as the light source, in this case, the sun. It’s subtle, but it’s there, and it shows on the target.
Sight Alignment
For review and clarity, sight alignment is simply centering the front sight between the notch of the rear sight so there’s equal light on both sides of the front sight. The top of the front sight is level with the top of the rear sight. Sight picture occurs while transitioning from sight alignment and placing the top of the front sight onto the target while maintaining sight alignment.
There are three focal planes to consider when shooting: your target, the front sight and the rear sight. The front sight is your main point of concentration and should be in constant focus, while the rear sight and target will be slightly out of focus. You can’t keep all three in focus, so don’t try. Focus on the front sight!
Same gun, load and set-up. The only difference was the sun’s position.
Sun Effects
The sun glare blurs the side of the front sight it illuminates, providing a brighter edge and leading to misalignment of the sight picture by making the front sight appear thinner. If the light source (i.e., the sun) is on your left, the left side of the front sight becomes brighter, making the front sight appear thinner on that side and your rear sight notch appear larger. You’ll subconsciously adjust your sight alignment by holding onto the sun to accomplish your sight alignment.
When the sun is directly overhead, it can also cause the front sight to appear shorter for the same reason. This will cause a higher point of impact than usual from your regular sight alignment. In extreme cases of sun glare on the front sight, it’s hard to establish a sharp sight picture, which forces the shooter to concentrate on the target because we want to see something in focus. This leads to poor accuracy. Sloped or rounded front sights can cause a “mirror effect” as they reflect the sun’s glare directly back to the shooter’s eyes, making sight alignment difficult.
Undercut front sights help with sun glare.
True Story
My own club range has shooters facing south due to natural barriers and the lay of the land. Unfortunately, the sun sweeps the horizon from left to right. During extended shooting sessions, it’s not uncommon to see bullet impact, or groups, move with the sun. Shooting sessions lasting 2-3 hours can move the point of impact several inches on bright days. On cloudy days, the effect is minimal.
Fixes
The above carbide lamp story mentioned above, or aerosol “sight black” can be used to combat the sun’s glare, as can black “sharpie” markers. Also, hooded front sights or sights that are undercut can help reduce glare. If you can, adjust your positioning. Different filtered glasses can also help.
Once you understand how the sun can affect your shooting, it’s easy to compensate, so your point of impact isn’t influenced as much. Knowing why it’s happening is more than half the battle. There are two kinds of light — the glow that illuminates and the glare that obscures.
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