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Most everybody probably knows this but just in case ...

I went online to refresh my memory as to the formula to calculate the amount of sight movement needed to affect a certain amount of impact change on the target. It's a pretty easy formula but it escaped my memory. I found this online calculator and it works great!


It took me longer to measure the displacement of the fired groups and the sight radius (3.46 inch by the way) than to input the data and get results. Here's what I calculated for a new P365 I was breaking in on Friday.


RangeDisplacement in inchesAdjustment Needed
3 yards (108 inches)0.550.018
5 yards (180 inches)0.650.012
7 yards (252 inches)1.290.018


So, I have a very linear displacement as range increases, which is what we want! So I'll slap on the sight pusher and give the rear sight a nudge of say 0.016 inch and give it another whirl. I should be pretty much dead on, and plenty close enough for the belly gun the P365 is.

It does shoot low at the same ratio as it shoots left, but I'm not going to mess with a front sight height change, especially when most folks tend to shoot high in SD situations anyway. I can live with an inch or so low at 7 yards if the windage is spot on.

I hope this helps and someone finds the calculator handy.
 
The equation is based off similar triangles. Basically the ratio of sight misalignment over sight radius is equal to impact misalignment over distance to target. Rearranging this equation to find the distance to move the rear or front sight you get,

Sight misalignment = (sight radius)*(impact misalignment)/(distance to target)
 

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