This was made a "Sticky Note" on BTB - Good Stuff!This seems to get asked most often with lever gunners...are a lot of rear sights being changed for reciever sights... it seems that the front sight is often the wrong height to make us happy.
(OK...math guys...know the equation is simple, but I get frustrated trying to get the computer to make those equations readable and we aren't all math guys...some of us are alergic to equations.)
Need a ruler and a calculator
1. Measure the distance between the front and rear sight....will call this (S) for sight radius.
2. Shoot the gun at a know range and measure the amount of change needed to get the impact where you want it...will call this (D) for the distance from the point of aim.
3. Convert the distance to the target to INCHES..will call this (R) for range.
Now to get where you want the bullets to go:
Divide D by R.
Multiple what ever you got above by S.
Lets run through one. Have a rifle that is shooting 6" high at 50yards. The sight radius is 20". I'd like it to hit exactly on at 50 yards.
1. (S) is 20"
2. (D) is 6"
3. (R) is 1800" (50 yards = 150 feet = 1800 inches)
So D divided by R = 6 divided by 1800 = .00333
And .00333 times S = .0033 X 20 = .0666
(Real world time.... .07" would be close enough.)
Which means that I need to move the rear sight DOWN by that amount to get to zero
or
Move the front sight UP by that amount to get to zero.
or
Change one of the sights (the front for a higer one in this case, the rear for a lower one) by the same amount.
So far so good.
But you'd really want the sights to not be bottomed out or topped out...would want some adjustment in both directions.
Would be better to set the rear sight in the middle range, and start the process over again...getting a new (D) number and running through the process to get you sight change in order to put you on target AND have some "fiddle room" for loads that may shoot differently.
By Ribbonstone
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Imashooter2 from MO put Ribbonstone's formula into Excel. Just plug in your numbers.
http://mywebpages.comcast.net/imashooter2/frntsite.xls
