Windage adjustment

[chawbeef]

Wondering how far to adjust my rear sight initially?? My rifle was shooting about an inch to the left at 45 yards and I tapped the rear sight over .005 inch to the right. Any thoughts on what difference this could make?? .............Daniel

 

[Flint62Smoothie]

You can use the mathematical equation of Tan Theta = Opposite / Adjacent. As the angle is the same between the sight offset (front to rear) and that of the rear sight to the point of impact, being 1" off at 45-yards.

We'd need to know the distance, in inches, from your rear to the front sight. Call this X.

Tan Theta = Opposite (1" at 45-yards) / Adjacent (1260" + X", for 45-yards expressed as inches, plus sight span).

This will tell you the exact distance your sight needs to move.

 

[Flint62Smoothie]

This is an EASIER explanation:

You can use the mathematical equation where the [amount the rear sight needs to move in inches] / [distance between the sights in inches (assume 22")] is the same as [1" off at 45-yards] / [1642" (45-yards x 3 x 12 = 1620 + the sight distance)].

In this example, it is X/22 as 1/1642. You cross multiply to get 22 = 1642X. Divide both sides by 1642.

This gives you X = 22/1642 or ~ 0.0134".

So assuming 22" between front & rear sight, you would need to move it to the right 0.013 of an inch to move the bullet 1" at 45-Yards. That's about 3 thicknesses of a piece of paper, i.e., not much.

 

[hanshi]

I hate math; I just do it by trial and error....mostly error. :idunno:

 

[Zonie]

To figure out how much to move the sight if the group needs to be moved 1 inch at 45 yards, measure the distance between your front and rear sight.

Multiply this measurement times 0.0006

If the distance between the sights is 22 inches we have, 22 X .0006 = .0136 or rounding it off, .014.

If the distance between the sights is 28 inches we have, 28 X .0006 = .0173 or .017

Both of these answers are about 1/64 of an inch.

The 0.0006 value is good only for a movement of 1 inch at 45 yards. For other corrections or range differences do the following:

Figure the distance to the target in inches. ( In your case,45 yards X 3 = 135 feet X 12 = inches = 1620).

Divide the distance the impact on the target needs to be moved by that first answer. (In your case 1 inch divided by 1620 = 1/1620 = .0006)

Multiply this second answer times the distance between the sights on your gun.

Figuring another situation, lets say the shot was hitting 7 inches low at 85 yards.

85 yards times 3 = 255 feet X 12 = 3060 inches.

7 inches of error divided by 3060 = .0023

Multiply this .0023 times the distance between the sights.

Let's say the sights are 25 inches apart so we have 25 times .0023 = .057 (or about 1/16 inch).

Raising the rear sight 1/16" will bring the group up to the center of the target.

See? The math isn't so hard to do after all. :grin:

 

[chawbeef]

Thank you Gents, since the distance between my sights is 25 inches and the distance from the bull to the center of my group is actually 1.25 inches my calculations come out to .0189 so I think I will try moving my sight over another .010 for a total of .015 and fire another group.
I like math, especially when someone provides me with a formula. :hatsoff: ...........Daniel

 

[azmntman]

:youcrazy: Go shoot it and report back, using these formulas is great, I guess, but since it ain't guaranteed exact GO SHOOT IT AND MOVE IT MORE/LESS.

 

[Eric Krewson]

My formula for moving the rear sight it to mark its position, tap it until I see a slight movement, take a shot and repeat. If my group shows I moved it to far I reverse my former procedure.

 

[azmntman]

Good idea

 

[hanshi]

In Mike Bellevue's video he taps the rear sight several times (trial and error) to get it on target.

 

[Col. Batguano]

Don't forget that you can move either or both sights to obtain your correction. A lot of times, it looks a little goofy to have your front sight dead centered, and the rear all kittywumpus to one side.

You can move the front to be slightly off center one way, and then the rear to be slightly off center the other way and a lot of times it isn't even noticeable.

 

[chawbeef]

Don't forget that you can move either or both sights to obtain your correction. A lot of times, it looks a little goofy to have your front sight dead centered, and the rear all kittywumpus to one side.

You can move the front to be slightly off center one way, and then the rear to be slightly off center the other way and a lot of times it isn't even noticeable.

Thanks Col. :hatsoff:

 

[Vaino]

I've found that putting both sights centered w/ the sides of the bbl by using a depth mike comes pretty close to the bullseye at 25 yds. Some slight tapping of the rear sight and it's right on. Using mainly Rice and a few Colerain bbls, I've never had to mess w/ the front sight for windage......Fred

 

[chawbeef]

Thanks Fred. :hatsoff: ................Daniel

 

[Grimord]

I have just the opposite problem. My rear sight is a fixed peep sight with vertical adjustment only. I have to move the front sight for windage adjustments. Right now, the blade of the front sight is in line with the left barrel flat in order to center the target at 25 yards. It looks terrible, but it is the only way I can get the gun on target, unless there is some other way that I am not aware of.

 

[Artificer]

OK, here is an age old adage that helps one adjust nonadjustable sights correctly.

1. Move the front sight "into" or towards the group. IOW, if the group is to the right of the target, move the front sight to the right.

2. Move the rear sight into the center of the bullseye. IOW if the group is to the right of the bullseye, move the Rear Sight LEFT or into/towards the center of the bullseye.

OK, there are two things you can do in your situation. The first is widen the rear notch in the direction you want the group to move into the bullseye. Now, that may not provide enough windage, though. So if that's the case, get a blank Rear sight with no notch and file the notch towards the center of the bullseye from where you group is hitting OR weld up the notch to cut it so it winds up centering your group OR low temp silver solder a piece of steel maybe 1/32" thick to the back of the rear sight so the original notch is covered and then file a new notch.

Gus

 

[Grimord]

Unfortunately, my rear sight is a peep sight with only vertical adjustment.

 

[Artificer]

Oops, sorry I missed that.

Is the muzzle of your rifle flat and perpendicular to the bore? If it is angled, that could be throwing the shots off right at the muzzle.

If not, then it sounds like you will have to get a replacement rear sight where the peep is adjustable left and right.

Is the peep sight barrel mounted or tang mounted?

Gus

Edited to add: If barrel mounted, is it mounted in a dove tail or the base screwed on?

 

[Grimord]

The peep sight is mounted to the tang. I never thought to check if the top flat of the rifle is perpendicular to the bore. Not sure what would be the best way to check that, but i could see where that could cause a problem. The index marks for the breech plug and barrel line up.

 

[Artificer]

The peep sight is mounted to the tang. I never thought to check if the top flat of the rifle is perpendicular to the bore. Not sure what would be the best way to check that, but i could see where that could cause a problem. The index marks for the breech plug and barrel line up.

Actually, it is the face of the muzzle that must be perpendicular to the bore, not just the top flat.

However, if your barrel is not swamped or tapered at the muzzle, you can check it with any kind of a precision square by laying the square on the three top flats and seeing if the face of the muzzle is perpendicular.

If your barrel is swamped or tapered at the muzzle, the way to check it is to turn a larger round piece of round metal stock in a lathe so the end just enters the bore, but cut/leave the shoulder (that is not turned down to bore size) perpendicular to the smaller diameter you turned to just fit the bore. When you put the smaller diameter end into the muzzle, as long as the light you can see between the larger shoulder and the muzzle face is the same all around, the muzzle face is perpendicular to the bore. If not, then you will see more light on one side of the shoulder to muzzle face. You might be able to use hard wood turned in a lathe to do the same thing, but it won't be as accurate as if you used metal.

There may be another way to check this that I cannot think of right now, that doesn't require machinist tools. If I think of something else, I will come back and post it.

However, if your barrel came from an American Rifle Barrel Maker, I doubt the muzzle face is going to be off as much as would cause your problem. Now, if someone shortened the barrel after it left the maker, then it could be off that much if they did not correctly cut/file the muzzle face perpendicular to the bore.

Not sure if you would want to replace the tang sight, but in the group listed on this page from Brownell's has some peep sights that are windage adjustable: http://www.brownells.com/rifle-parts/sights/index.htm?k=peep+sight&ksubmit=y

Gus