Front Sight calculator

[timski]

Front Sight Height Calculator


Frequently a change in the rear sight of a rifle means a taller or shorter front sight is desired. Determining the desired height is a simple calculation that is explained below.

1.Shoot a group (at least three shots) with the current front sight. This can be done from any known distance. Convert the range to inches. (i.e. 100 yards is 36X100 or 3600 inches)

2.Measure the distance the center of the group is from the desired point of impact in inches.

3.Measure the distance from the front sight to the rear sight in inches. This is called the sight radius.

4.The change in height needed is calculated by multiplying the desired change from step 2 by the sight radius in step 3 and dividing by the range (in inches) that the group was fired at from step 1.

For example:

Let's say our rifle shot 10 inches high at 100 yards and the sight radius of our rifle is 23 inches. We can calculate the amount of change we need in the front sight as follows:

Change = 10 inches X 23 inches = .064 inches or about 1/16 of an inch.
3600 inches

Now to order a front sight the correct height, You measure the height of the front sight on your rifle from the bottom of the dovetail to the top of the sight, add the change calculated above and ask for that height. Use a caliper or micrometer to measure with since you need to have an answer in thousands of an inch.

It is important to note that front sights adjust the opposite direction you want to move the point of impact. In the example above we were shooting high so we needed a taller front sight. If we were shooting low we would want a shorter front sight.

Rear sights adjust in the direction we want the move the point of impact. If we want to move the point of impact to the left we move the rear sight to the left.

[jackruff]

This is a good example of an application of trigonometry and algebra that might stimulate an outdoor-minded ninth grader who hasn't previously shown any interest in mathematics. The measure of any angle is the same, no matter the radius.

[Cascade Jinx]

The formula used in the Skinner Front sight calculator can used for various ranges and is depicted as follows in the Lyman Reloader Manual (Appendix B):

M= (D/R) x S

M= Movement in inches needed to correctly zero your sights

D= impact deviation in inches (how far off from the aim point to the point that the bullet is hitting)
R = range in inches
S= sight radius (distance between sights)

Example: firearm is hitting 6 " low at 50 yards

D= 6" R= 50 x36 =1800 inches (for 100yds it would be 100x36 = 3600")
S=20"

M=6/1800 x 20 = .067"

0.67 " of sight adjustment is needed to zero the firearm.


(Note: For most 20" barrels on Marlin 336s, S= about 16 Inches)

[Fomdiddle]

Thanks Tim. I will be ordering from you shortly. Fom

[FTG-05]

Good stuff for when I order my rear sight.

Do the WWG or Skinner rear peep sights *usually* require a new front sight?

Thanks,

Al

[timski]

For Skinner sights, a taller front sight is necessary about 20% of the time on 1895 and 336 rifles, 50% of the time on 1894 and 20% on model 39 sights. These are based upon reports from customers over the years.
I'm not sure on WWG.

[FTG-05]

My bad, I just realized this was a thread in the Skinner sights forum.

[timski]

That is not a problem.

[biggog]

When Cascade Jinx says the sight distance is 16" is referring to the factory sights? If you put a Skinner sight on your gun the sight distance would have to be 20 some inches. I'm curious about these figures because I just put a Skinner sight on my 336 and I'm wondering if I'll need a new front sight.

[Fomdiddle]

Just measure the distance between your current sights. What the factory sight radius was has no bearing if you have changed already. Fom