Effect of sun angle on iron sights

[GJM]

This morning, my wife and I went to the range specifically to check our zero on several pistols at 25 and 30 yards. We each were using our own IPSC cardboard, using the head as our aiming zone. I shot four pistols, and all had 2-3 inch groups on the head, fine in elevation, but about 1.5 inches right of center in windage. My wife has a simliar POI deviation to the right (she is lefty and I am right handed).

The sun was strong, bright and from the right side of the target. When I shot kitty corner across the bay, with a resultant different sun angle, using an eight plate, painted white at 35 yards, I didn't notice the POI deflection. Google says the following on the concept of left or right effect of the sun.

with the sun to your left, it makes your front sight thinner. the left side of the front sight disappears making you compensate by holding more to the left which shifts your POI to the left.

This make sense?

[voodoo_man]

I have been told by various people that sometimes you shoot better in the morning than in the afternoon, sometimes the opposite, depending on where you are in the world and where the sun is in relation to your shooting position.

I've never actually seen it affect me.

[LSP972]

It affects different folks in different ways. I am particularly sensitive to this; to the point that I kept a logbook of each range we shot on the PPC circuit, noting time of day/other conditions and what sight adjustments I needed at the long line (50 yards). Depending on the angle and brightness of the sun, I sometimes had to take as many as six or seven clicks of windage to stay in the ten ring.

This is complicated further if you are using a vertical surface for support. You can get what's called the "barricade shadow"… IOW, your front sight is in bright light and the rear in shade, both in either, or vice versa. My detailed notes allowed me to crank in the necessary adjustments before the stage/string of fire began.

Now… keep in mind that my target was a two inch by three inch oval. At the High Master level of that game, the winner can be decided by X count. The ten ring is a bit more generous (3" X 4"), and points always beat X's, but the year I won the state championship it was by ONE X.

Also remember that I was dealing with rather delicate precision sights, fully adjustable and repeatable… not, IOW, what you're going to find on your average service or concealed carry handgun. Hell, we used to smoke them with a carbide lamp to kill any reflected light.

The condition exists, one should be aware of it, and have it in the back of your mind. But you cannot plan for it unless you're in a static environment where you KNOW what the conditions will be, such as a competitive venue you have shot before, under similar conditions and at the approximate same time of the year. Believe me, that latter makes a difference, because if the sun is in a different place in the sky… things change.

What I'm saying here is this: be aware of it, but don't get wrapped around the handle about in terms of preparing your defensive stroke/response. Even if you're trying for a head shot, your target is much more generous than a 2" X 3" oval.

Also know that some folks are simply not affected much, if at all, by this. My two man team partner, who was every bit as capable as I was, never bothered to adjust his windage because of light conditions. Everybody who is serious about it will make elevation changes between the short and long lines, due to the fact that wadcutters have a rainbow trajectory. But this guy was not bothered by side light conditions. If he and I could have ever got our feces consolidated on the same day, we could have won the national two man team event. That takes a pair of 598s or 599s (out of 1200 possible; 2 X 600). One time I shot a 598, he shot a 594; fifth place for us. The following year, he shot a 599 and I hosed out a 593; sixth place. Man, that was frustrating.

So yes, the phenomena is real. How it affects you (collectively speaking) simply depends upon your eyes. The rule of thumb is, the more perpendicular the light is to your direction of fire, the stronger the effect. IOW, if the sun is at your back, the effect is minimal or not there. If the sun is at your three or nine o'clock, it might indeed cause some displacement in your shot group/hits.

This is why a properly laid-out range, in our part of the world, always should face to the north; because the sun is usually in the southern portion of the sky.

All of this matters to a PPC or conventional pistol (bullseye) shooter. And to dialled-in guys who want to cover every base, like George. Most other folks either haven't a clue about it or don't care.

And they usually get by…

.

[BN]

I've seen that. Sometimes the sun can wash out one side of the rear notch also. If I'm fine tuning the sights, I like to do it on an overcast day or from a shaded shooting position.

[Wondering Beard]

I believe it's one of the reasons (effects of the sun) that some people don't like gold beads in their front sights.

I like them but I'm one of those folks who "get by" :-)

[ACP230]

I hadn't noticed it before but last time I was at the range I started shooting high
when I went from low sun into the shade of the range house. Was doing a
walk back type drill at the time.

I have not noticed windage changes due to light conditions with pistols.
It may have been a factor, at times, when I shot NRA Highpower Rifle Matches.

[GJM]

With the strong right morning sun, this is the result of successive five shot groups with three different Glock 19, a 17, a 239 and a 229 at 25 yards, with pistols that I thought were zeroed.

[GLB]

It has always been my experience that with a strong sun the POI follows the direction towards it.

[SLG]

GJM,

The basic rule is as you read. The sun pulls the group towards it. Doesn't always work that way, but it's a good rule of thumb.

eta... I always try to zero on a cloudy day. Makes life easier if you can swing it.

[GJM]

Can you imagine how this thread would have gone, shooting a Glock, if the sun was on the left?