Yesterday I was running my monthly club shoot, 48 rounds fired at 10 and 25 yards. One of the shooters, who had never shot this match before, is a fellow police officer. At the 10 yard line he was very accurate with his privately owned Gen 4 G17.

We moved back to 25 yards and suddenly his groups were off to the left by about 10". After the match he mentioned drifting his rear sight, but couldn't account for the "sudden" shift in POI.

At that point I jumped in and mentioned that the range we were shooting on faced east, it was 11 am, we were on the sunny side of the range and, just on 6 weeks past the winter solstice, the sun was still significantly to the north. All that meant the sun was shining on the left side of his front sight leaving the right side in shade.

I suggested that he was using visible light to gauge his front sight being central in his rear sights and the lighting conditions at the time were causing him to move his front sight, and groups, to the left.

He, and others, were a bit sceptical of this so I moved a target into the shade and had him shoot a group at 25 yards. The group was central in his target, and he admitted there might be something to what I was saying.

Now I thought all shooters knew about the tricks light can play on a front sight. When ever I shoot a stage I look for where the light is coming from and if I can't shoot in 'neutral" light or shade I concentrate on keeping the front sight central in the rear sight notch without compensating for light/shade issues.

Or am I just strange?

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View from down under