How to Figure Height Adustments on a Rifles Front Sight

Big John Denny · December 31, 2005, 04:36:29 PM

Folks have posted before about various sighting problems on their rifles. A problem that occurs sometimes is when the rear sight is fully elevated or depressed and the shot group is still either too high or too low from your point of aim. To fix this problem to bring your rifle to point of aim you either have to lower or raise the height of your front sight. This is not a real hard thing to do, and we who have to shoot Italian made muzzle loaders in N-SSA shoots know it all to well, but the same formula works for all fixed sighted rifles.

Lets say you've tried to sight in your rifle at 25 yards, but after making all the adjustments you can with the rear sight you're still shooting 6 inches high at that range.

You first have to measure the sight radius of your rifle in inches. This is not hard. Take a tape measure or even a yardstick and measure from the rear of the front sight blade (the part of the blade you see when aiming the rifle), not the base of the dovetail but the base of the actual blade itself, to the front of your rear sight (the part of the sight you see when aiming the rifle), and record that measurement in inches. For this example lets say the measurement is 20 inches.

The formula for determining the amount of front sight correction is this:

Amount of Error in inches ( In this case 6 inches) multiplied by the Sight Radius in inches (In this case 20 inches) divided by the Distance to the Target in inches (In this case 25 x 36 (inches in a yard) = 900 inches). OK lets do the math (with a calculator)

6 x 20 = 120 ; 120 / 900 = 0.13 inch

In this case, if you were shooting 6 inches high at 25 yards you will need a front sight that is 0.13 inches taller then the one on the rifle now.

If you were shooting 6 inches low at 25 yards you will need a front sight that is 0.13 inches lower then the one on the rifle now.

Remember, when adjusting the front sight you always move it opposite to your hit group on the target you're sighting in on for your chosen distance. Make the front sight higher to shoot lower; lower to shoot higher; move it left to shoot right; and move it right to shoot left.

This formula will work for whatever distance you wish to sight in for. I chose 25 yards in this example under the premise you were sighting in a CAS main match rifle, and I doubt you'll ever see a target on a main match beyond 25 yards. The final corrective figure will change based on your chosen sight in distance for which you wish to shoot point of aim.

For instance, if you wanted to sight in at 50 yards (50 x 36 = 1800 inches), the amount of correction would be 0.066 inches.

I always use a caliper, either dial or digital, to measure the height of the front sight. Be cautious in removing the metal from the sight. I suggest removing a little at a time and firing the rifle again before going further. Metal is easy to remove, but real hard to put back.

Hope you find this information usefull.

Presidio · December 31, 2005, 08:59:34 PM

Thank You, Big John!

Ya' jest fixed muh P. O. A. with muh rifle. Now, Im'a gonna try it on muh pistolas and see if'n that helps me any.

Probably not, Im'a poor sighted cowboy ta' begin with . But. it's worth a try!

Big John Denny · January 01, 2006, 12:15:18 AM

Presidio, if you always use the same load in your pistols it will work on them too.

Hemlock Mike · January 01, 2006, 06:37:11 PM

I worked out the "formula" myself with my RV about 7 years ago. It said to remove 0.040" of front sight.
I stopped at half that and was right on. It's easier to remove than replace !!!

Go slowly and try it as you go. Be real careful with that Dremel tool

Mike

Cyrille · March 06, 2006, 05:10:04 PM

I've just read suggestions on how to fix the 'elevation' on a rifle's front sight do the same rules apply for a revolver? When I shoot my Ruger Vaquero, Old model I aim real low and sometimes hit the target 2 or 3" above the center, but I have to say that the majority of my shots are within 1" above or below the "bull." I've tried filing the front sight down a bit but that does not seem to help my POA if I aim directly at the 'bull' any any other suggestions? I have been shooting 6.0 to 6.3 Titegroup behind a 200gr. RNFP

Cyrille · March 06, 2006, 06:18:52 PM

Woops, seems I made a boo boo but the dang thing always shot high since day one, I guess it's like someone said in an earlier post, " most cowboys learned to shoot what they had." The gun shoots high, allays did, so I'll jest haffta shoot low.

Big John Denny · March 06, 2006, 07:21:50 PM

Cyrille, sorry I did not get back to you sooner. The formula will work for pistols too, but you have to have groups in the same area first. It may be that your problems are not entirely with your sights. You may have operator problems like inconsistent sight picture, or grip problems.

To determine if those things are the problem, the best way is to fire from a sturdy sandbagged rest or a Ransom Rest. If the fired rounds then group in the same place consistently, you will be able to apply the formula and adjust front sight height accordingly

Cyrille · March 06, 2006, 10:55:14 PM

Perhaps it's the distance; I've shot from a pistol rest @ 10 meters/yards and grouped within 2" of the "bull" w/ a 5 shot string but I still had to aim low to do that. I've shot without the rest at varying distances from 21 to 50 ft. and stay well within the "kill' area on a 1 x 2' sillhouette with a 5 shot string but I have always had to aim low and slighty to the right.
If I aim directly at the center mass I'm high and to the left.
Maybe if I dropped the powder charge a grain or two below 6.0 that could lower the POI could it not?

Big John Denny · March 07, 2006, 03:53:33 PM

Short answer is yes. You could also increase your bullet weight. 200gr bullets will usually shoot lower than a 250gr bullet using the same load in a 45 Colt. If you're only going to be using the pistols for SASS/CAS matches, I would concentrate on sighting in at the maximum distance allowed for SASS while paying strict attention to sight alignment and consistent grip pressure.

Cyrille · March 07, 2006, 04:41:48 PM

According to what was said in your last post I should be useing a bullet of lighter grain weight than 200 'cause my problem is that the .45 Colt Vaquero shoots above POA is that not correct?

Cyrille · March 07, 2006, 05:18:22 PM

I also want to ask just what is the maximum distance for revolvers at a Cas, Sass, NCOWS shoot? I have heard that it is "somewhere under 25 yards, but no definate distance could I find.

Big John Denny · March 07, 2006, 07:35:38 PM

This is right from the SASS Match Design Guide.

Recommended Sizes & Distances
Listed below are the minimum target size and distance standards. Designers are encouraged to use larger targets at the distances indicated whenever possible for main stage scenarios. Measurements of targets do not include appendages, and must offer continuous steel for compliance. Special care should be taken when using paper targets, stop plates, fixed or flying clay birds, and other non-conforming targets due to the additional time necessary to reset them after each shooter.

Pistol targets

•   Minimum distance is 7 yards; maximum distance is 10 yards.
•   Minimum pistol target size is 16" x 16".
.
Shotgun targets

•   Minimum distance is 8 yards; maximum distance is 16 yards.
•   Minimum shotgun target size for 8 yards is 8" x 8" (MGM size poppers allowable)
•   Minimum shotgun target size for over 8 yards is 16" x 16" average.

Rifle targets

•   Minimum distance is 13 yards; maximum distance is 50 yards.
•   Minimum rifle target size is 16" x 16".

You will find smaller rifle targets at some matches because most match stages are not able to be fired on a range of 50 yards. I usually see diamond shaped rifle targets at some matches shot at the minimum distances.