Hey guys,

If anyone's interested, I wrote a simple program that calculates the amount of iron sight adjustment needed to achieve the necessary change in bullet impact at any range.

I did this after getting REAL tired of my M96 Swede shooting my handloads 12" high at 100 yds, and I needed to tell my machinist friend how tall I wanted my front sight made.

All the necessary info is already there for both the M96 & M38 Swedes, but it will work with any arm - all you need to do is to measure the sight radius (distance between front & rear sights) for whatever gun you have. It works very well - put my M96 bang-on, but of course everyones rifle is different.

E-mail me if you want it (free for my fellow shooters of course!) Sean.Kettley@nscc.ca

Cheers,

kettlesd

Hello,
I believe you are making reference to how much up or down adjustment, of front sight are you not?? The formula for determing this used to be published in the Brownell's Catalog. Been a while, but believe it is still in there. This adjustment does require that your rear sight be at mechanical zero or if it has been moved, the adjustment of the front sight blade would not hold true. Old rule of thumb used for years was .008" adj. up or down would yield approx. 1" of change in point of impact at 100 yards for most rifles. Certainly not true for all situations, but works for a great many.
Once you have established your mechanical zero, elevation wise, the trick is determining the elevation for ranges beyond the 100 yard mark. I also shoot military issue Swedes, but as in all situations, you alter the load or ballistics of the round being fired, those graduations on the ladder sight do not correlate. In short,those sights are load specific
Again, rule of thumb, but for each 100 yards, add 3 minutes of angle elevation adjustment out to approx.700 yards. Rule changes at that distance and requires more. Should mention that the elevation adjustments are accumulative and to get you out to say, 700 yards from 100 yard zero, will take appox. 18 additional minutes of elevation.
Your formula info is definitely good info, but so few shooters utilize mechanical sights anymore that it is almost a lost art except for match shooters or those shooting miliary style weapons in matches. Favor Center!!
dsiteman

Yes, I was referring to the up/down/left/right adjustments for front & rear iron sights.

We have military shoots at the club I belong to, and almost all the shooters there handload. Accordingly, a great many suffer from their sight elevation increments not corellating with actual point-of-impact.

Since I am studying computer programming in University and I had to come up with a project, I decided to do something that would be useful to me in the real world!

I decided to compile known formulas into a simple program that would give me precise elevation & windage adjustments. The rule of thumb of .008" adj. up/down to yield approx. 1" of change in point of impact at 100 yards would work for most rifles with a standard 22"-24" barrel. As the sight radius is a key piece of the calculation, I wanted to calculate for ANY firearm with iron sights - namely my M96 with a 29" barrel and subsequent longer sight radius or my pistols with obviously a much shorter radius.

I have a simple calulator I came up with in a MS excel spreadsheet you could have if you wanted. You must enter in 1. Distance to target (yards) 2. Sight plane distance (inches) 3. The amount to move the point of impact (inches) Then the result is how much to move the sight (thousandths). I could email it. If you want it drop a note at xtrapx55555@xyahoodotcom (remove the x's and replace dot with .)

Just about all the iron sight manufacturers (Lyman, Redfield, etc) pack a chart and instructions for adjusting the height of sights in the box with their sights. I've never looked, but I would assume that the chart is also available on their web sites.

Rick

My son wrote one for me years ago based on the old formula that has been around for decades. His ISC was incorporated into Ballistic Basics 7 or 8 years ago and then into Totally Ballistics programs last year. That formula ia fool proof so long as careful measurements are taken and no guestimates are used. Junk in, junk out.

IM=D*K*SM/SR

IM=impact movement
D= distance (In inches, yards, or meters)
K=constant=12 for inches, 36 for yards, 39.4 for meters
SM=sight movement
SR=sight radius

There is a "formula" in the Brownells Catalog also.

Still a problem??