Front sight windage adjustment

[Lone_Gunman]

I know if I move the REAR sight to the right, it moves point of impact to the right.

But what about moving the FRONT sight? Doesn't moving the front sight in one direction cause the point of impact to move in the opposite direction?

In other words, I have a rifle that shoots to the left. The front sight is windage adjustable. Which way do I need to move the front sight?

 

[Pilgrim]

Front sight opposite the direction you want the impact point to move.

Pilgrim

 

[Husker1911]

Concerning front sight adjustment, it's easier for me to remember to "chase the bullet." That means if the rifle is shooting to the left, I chase the bullet, and move the front sight to the left.

Or just do the opposite what you'd do with the rear sight.

 

[230RN]

The hinge point (fulcrum) of a lever system.

Don't forget that's sometimes a pretty small amount, especially for handguns.

For either sight, using inches...

Distance to move sight = "A"
Distance to move impact point on target = "B"
Distance from front sight to rear sight ("Sight Radius") = "C"
Distance to target in the same units = "D"

Then, if all in the same units, say inches, you can use the proportion,

A / B = C / D

("A is to B as C is to D.")

Transposing the quantities, with Distance to Move Sight ("A") as the unknown,

A = (B X C) / D

Example 1:

My 1911 with a sight radius of 6.5 inches shoots four inches to the right at 25 yards. How far should I drift the rear sight?

Distance to target in inches = 25 yards X 36 inches in a yard = 900 inches

So A = (4 X 6.5) / 900

A = 0.029 inches to the right for the rear sight.

Example 2:

My .22LR rifle with a sight radius of 14 inches shoots four inches to the right at 25 yards (same as in the example above). How far should I move the rear sight ("windage")?


So A = (4 X 14) / 900

A = 0.062 inches to the right for the rear sight.

Notice how much more this is for the rifle with a longer sight radius than the pistol.

In trying to visualize what direction should either sight be moved, it helps to hold the gun and imagine the front sight as a "hinge" as you watch where the muzzle points while you rotate the gun from side to side around the "hinge point" formed by the front sight.

The fact that these are such tiny distances can lead to confusion in adjusting sights because it is so easy to "overdo" the adjustments.

So then you "overdo" it in the other direction and you end up chasing the impact point around all day long.

 

[BobMcG]

Don't forget that's sometimes a pretty small amount, especially for handguns.

It's a pretty small amount even with a rifle!

 

[230RN]

'T'sall relative

Not when you've been a precision machinist for years and years and "a tenth of an inch" means 0.0001 inches.

Still, they're small distances when you think of pounding on a sight with a brass rod* and a hammer to move it --what you say is twue, twue, vewy twue.

It helps to use a precision calibrated hammer.

----------------
(* or whatever)

 

[rangerruck]

it does the exaact opposite, than when moving the rear site.

 

[ripcurlksm]

Great post 230RN, its safe to say that of all I have learned in math, I have used proportional equasions the most in my life....now I can add it to firearms as well.

 

[Kruzr]

The way to remember is FORS. Front Opposite, Rear Same (when talking about POA/POI.)

 

[Mal H]

Not when you've been a precision machinist for years and years and "a tenth of an inch" means 0.0001 inches.

I've been using precision instruments and fine micrometers for practically all my life and I've never heard a "tenth of inch" to actually mean a tenth of a thousandth of an inch (1/10th mil). To me a tenth of an inch is 0.10 inches. Is that accepted shorthand in your shop?

 

[ripcurlksm]

Maybe he means he can get 1/10th of an inch to within .0001 of that measurement?

 

[Remander]

There is some good info with pics over at surplusrifle (closing soon) about adjusting SKS front and rear sights, but the principles apply to all guns.

http://www.surplusrifle.com/sks/sights/index.asp

 

[230RN]

In our shop, "3 tenths" meant 0.0003 inches, or three ten thousandths of an inch. Might just be a regionalism, though.

 

[hksw]

Going back to the original question, sometimes drawing out the problem/question helps.



The illustration also goes for windage. Just go the other direction if the POI is on the other side of POA.

Difficult to measure the changes in movement of the sights in tens, thousandths, and ten thosandths of an inch at the range. Just adjust, shoot, re-adjust as needed.