Is there a formula for setting a vernier sight?

[CaptainKirk]

In the video I posted, you will notice he has his calculations tabulated on index cards. Naturally, this will change if you alter your load composition in any way. But you should still be close.

 

[French Colonial]

Ok kids here is the formula
Sight radius in inches times the distance to move the POI divided by the distance to the target in inches equals the amount of adjustment

25 yards is 900 inches
50 yards is 1800 inches
100 yards is 3600 inches

example, my Chambers rifle is 37" between the sights and I want to move the impact up 1" at 50 yards

37" X 1"/1800= .0205555

example number two my Jaeger is 20" between the sights and I want to move the impact up 1" at 25 yards

20" X 1" /900=.022222

This is all great, but if your using a vernier sight I assume you are not shooting PRB's at 25 yards, you are probably shooting conicals at 500 plus. Yes the formula still works........but!

As I stated before there are to many variables for it to be exact. Is the wind behind you or in your face, more than likely quartering at some angle. Mirage? And as stated before even the humidity from a 20% to a 90% (yes we get those in S. IL) will cause changes.

If your going to use a vernier at distance, get a notepad that fits in your shirt pocket, write down your settings at every distance every time you shoot and fine tune your settings the day you go for score.

 

[dave951]

Lots of math going on here guys, but here's the actual info.

Yes, you can calculate the amount to move the sights to obtain a given amount of movement on target. That's simple math.

No, the markings on a venier sight DO NOT MEAN 1 MOA or 1 MRAD. They are ONLY a witness mark to show how far you have moved your sights. For those marks to mean anything, the front sight will always have to be at a set distance from the rear and that's the crucial point you guys are missing here. It just is NOT a set amount of distance.

I HAVE a 50/70 roller with Lee Shaver Soule sights, Hadley eyecup, front globe and spirit level. One hash mark DOES NOT MEAN 1moa.

 

[BadDaditood]

It’s simple on my 40-70 SS Shiloh
54 = 200 yds.
Next week I’ll see what number 300 yds is…

 

[French Colonial]

Do you know how far your sights are apart? lets call this A
Do you know how much you need to adjust your impact? Lets call this B
Do you know the distance to your target? Lets call this C

A X B/C= adjustment.

Really guys c'mon....This is taught in grammer school

 

[Widows Son]

and I bet your powder is a lot better and more consistent than what was available in the good old days

That is the only part of your statement that I disagree with.

 

[ResearchPress]

When sight elevation is changed the graduations are a measure of how much you are adjusting the rifles alignment to the line of sight. For a known sight base how much to move the sights to change the angle of the rifle by 1’ or 5’ or whatever you need can be calculated, and the sights can be calibrated to that. Gibbs-Metford sights of the 19thC for example are calibrated in degrees and minutes and 5' elevation adjustment on the sights alters the alignment of the barrel to the line of sight by 5'. For a 36" sight base 1 minute of angle is 0.0105". Unless the sight used is made / calibrated for your sight base you will have a close approximation to minute of angle rather than a true measure.

How much difference this will make to the placement of the bullet on the target will depend on load and conditions. I shot at 900 yards at the weekend and had 4' additional elevation compared to last time I shot with the same rifle and same load, due to different wind conditions. A changeable head or tail wind will play havoc with elevation at long range.

Sight adjustment between ranges is not the same due to bullet trajectory. Metford's elevation tables in the 19thC and for a specific load show for example, 200 - 300 yards a 12' change in elevation, 500 - 600 yards a 15' change, and 900 - 1000 yards a 18' minute change.

Many long range riflemen will plot their shots on a target diagram with a minute of angle grid overlay - plotting the fall of shot will help in fine tuning sight adjustment to centre the group. Also keep in mind that we're talking about mean point of impact - you / your rifle may only be holding a 2' - 4' (or whatever) group.

Keeping a record of settings for the rifle / load / conditions helps. One rifle I used at the weekend I had only fired at 300 and 500 yards, but the competition was at 600 yards. I knew from experience / records the sight adjustments made for different rifles to go from 500 - 600 yards, so was able to make a good estimate. My first shot fired hit the bull and I ended up winning the competition. Keep a 'diary' for each rifle.

David

 

[nhmoose]

Wow to much Math! Love my smooth bores. Cant see a 1000 yards anymore anyway.