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There's this article online about sights. I ran it through Google translate, but the result made no sence, so I had to edit it quite a bit. Hopefully you get the idea.
Some comments:
You say circle inserts, so I use the same Word here, or just circle.
R/J shooters = recruit and junior.
Long and short barrels. the Sauer 200 str comes With barrellengths from 67 - 74 mm. http://en.wikipedia.org/wiki/Sauer_200_STR
Fieldshooting: In Norway a highpower match has 5 targets on various distances from i.e 90 - 600 metres. The targets are out in the terrain, so the shooters must walk from position to position. On the shooting position, they must judge the distance to the target and adjust their sights. The targets have irregular shapes, and various sizes. The normal way of jugdeing the distance to the target is by using the sights. If you know how big a certain target is in your "circle" at i.e. 100 metres, then you can judge the distance by how many targets will fit in the circle. Experienced shooters are very good at this, and are dead on all the time. Smallbore matches are shot at 100 meters, by junior and old shooters.

Here we go:


How to use the sights, and how to choose the right frontsight insert.

This article was previously published in Norwegian Shooter Official Journal . Author is former national champion John Olav Ågotnes

Targetshooting – circle inserts

What kind of circle insert size is best to use is a topic often discussed among shooters with strong opinions.
I shall give some rules of thumb for selecting circle inserts.
Young shooters often use too small circle inserts. This may be because the "young eyes " have muscles that can better adapt the intensive focus. However, it is often you sees signs that R / J - shooters use too small circle inserts .
It is easier to decide when the target is in the center when only a small clearance between target and circle. This is also very demanding for the muscles in the eye.
R / J - shooters with small circles often find that they shoot significantly better in the first series of shots than in the later. .
Shooters who shoot standing, where movement of the weapon is clearly greater than in lower positions, often prefer small circles as it is " easier to decide ." (when to pull the trigger).
A rule of thumb is to have a circle that provides a coverage width that is twice as large as the target . With a long barrel, that will say about 4.0 mm at 2-300 meters . Similarly, for 100 meters will be about 4.8 mm, then the target at 100 yards is 20% larger . When the target is easier to see, the closer the comes, it will be more natural to use about 4.2 to 4.4 mm at 100 meters with a long barrel. ( short barrel minus 0.2 mm) Those who are used to small circles will initially feel it’s difficult with larger circles.
What is interesting is not what one feels but what the result in the target shows . It is also easier to see your mistakes and “pull outs” with a normal circle than with a small one. It looks worse but the results are often better. It must also be noted that
nearsighted people use generally slightly smaller circles and farsighted use generally slightly larger circles

What do the best use?
.
It is always wise to see what the top shooters use . After speaking
with the elite of Norwegian target shooters , most use from 4.0 to 4.5 at 2-300 meters.
Wall thickness: The rule of thumb for thickness is 1/ 3 of the circle diameter.
I.e. from 3.6 - 1.2 and 4.2 - 1.4 . There is also much to be gained from switching circles under different light conditions . With the sun in the back and strong sunshine on the target, there will be an advantage with smaller circles with thicker walls.
Thicker walls offers better contrast. Similarly, if shooting in misty and cloudy weather, larger circle with thinner walls.

Choosing diopter hole.

Those who use weapons with Busk sights know that you can choose from six
different diopter holes . Only the three smallest should be used , because they provide diopter effect .The three largest is a peep sight.

Diopter effect.

When the diopter hole is about 1.2 mm or less, it provides the diopter effect.. Everything we see through the hole is then clear. For example , we see the circle
and target sharply simultaneously. Same principle as in photography. Using small aperture makes the image sharp in depth. Using the peep sight we must focus from circle to target constantly.
Another thing one should be aware of with peep sights is to have the circle in the middle of the rear sight to avoid different point of impact from shot to shot. The same applies to those who use variable iris aparture. The diopter effect disappears at about 1.2 mm. Bright light on the target can also be countered with color filters . Whether the color filter in iris or colored glass in spectacles . Gray or brown glass then gives the best effect. In hazy and cloudy weather many prefer a yellow glass / filter . Be aware that even if the contrast is improved somewhat, yellow glass filter away about 15 % of the light .

Fieldshooting

Unlike target shooting, one should use the same circle throughout the fieldshooting season . This is because two circles rarely provides the same POI, and in fieldshooting you have no test shots to correct for POI before shooting.
The template is here from 2.8 mm to 3.4 mm on both highpower and smallbore matches. In a highpower match, where one must judge the distance using coverage width of the circle ,it is advantageous to use a circle with as thin walls as possible, without loosing the clearness of the circle. It is then easier to see when the target touch the circle. With thicker walls, you can accidentally hide some of the target behind the circle without noticing it, with the result that you judge the distance to the target too far.

Summary

There is much to be gained by trying different circles untill the target looks good .
If you feel that you do not see the target clearly, it is difficult to achieve top results. Maybe you also have revealed that you should have been a trip to the optometrist ?
 

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I’d forgot the details about estimating distances with the sights, so I had to refresh my memory a bit.

To make this method work, you must have a circle insert of correct size. On 300 meters, a 100 cm wide target must fill the circle. It means that the target (in cm) covered by the circle X 3 = distance in meters.
This was a little bit unclear. the size of the circle insert depends on the barrel length. If you aim at a wall 300meters away, the front sight circle should cover a 100 cm wide part of the wall. That's the important numbers here. 100 cms covered on 300 meters.

To find correct insert size use this formula:

1000mm x distance from eye to circle insert (in metres)/ 300meters = circle insert size in mm


Now, go to this link. You’ll see the illustration with the circle inserts with the targets inside, and the examples.
http://www.skytterlag2.no/filestore/Skytterlag/Hammerfest/PDF-filer/feltkurs.pdf

You’ll need to know the exact size of the target, and this you will know during a match.
Aim at the target. Move the rifle so the target touches the side of the ring. Estimate how many targets can fit inside the circle. Be precice.


Ex 1: The pyramide shaped 1/3 figure is 50 cm wide. It goes 2,5 times inside the circle.
Covered area: 50cm x 2,5 = 125cm Distance: 125 x 3 = 375 meters.

Ex. 2: The stripe is 30 cm wide. It fills the circle twice.
Covered area: 30cm x 2 = 60cm, Distance: 60 x 3 = 180 meters.

Not so difficult once you got the hold of it. If you don’t have an insert that fits this formula, you can make your own table. Go to the excel sheet in the bottom of this link: https://www.dfs.no/opplaring/fagstoff/feltskyting1/avstandsberegning/

In the yellow box on the top you fill in the distance from your eye to the circle insert of you rifle, in meters. (sikteavstand), then the circle insert size in mm. (hullkornstr.) The table will now show you the distances to the various targets.
I.e. the top line is for the C-20 figure. It shows max distance this target can be encountered, width / height etc. C-20 is 20 cm wide. When it fills the circle of your front sight, the distance is 74 meters. When two C-20’s fit inside the circle the distance is 147 meters etc… This table is quite helpful when you’re in a match and only have a few minutes to set your sight.

Scroll down to see the fieldshooting targets. I think the same targets are used in Sweden as well, but I’m not sure. https://www.dfs.no/Documents/Skytterkontoret/Fagstoff/2012/Felt_arr_vei_lav.pdf

You will also need to make tables for sight settings according to wich ammo you use etc… But that is another matter.

Now, get out and start practicing.
 

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I found another interesting article. The Author is an optician, and specialicing in shooting glasses. this was originally printed in Normas newsletter for the Norwegian national match in 2010, but fortunately he also added it to his web page.

http://www.skytterbriller.no/?news=show&page=66

http://skytterbriller.no/index.php?parent_text=26&page=26

How important is vision in shooting ?


Vision and visual acuity has been discussed since peepsights / dioptersights came on .the market. ( picture of old shooter ?)

I'm so old and lucky that I had Oscar Sjöqvist as instructor when I took the three instructor courses through DFS . His book "Geværskyting” (Rifle Shooting ), also known as “The Red Bible” , is in many ways just as relevant today .
I was a fresh optician student at the time and had many wonderful discussions with Oskar .
He was very consious about exploiting the "dioptereffect " .

Dioptersight ( diopter ) is a type of sight for guns with diopterhole of max 1.2 mm.

From Wikipedia, the free encyclopedia
" " Dioptereffect is achieved by looking through a hole that is less than 1.2 mm in diameter. If you look through a dioptersight at a target, the frontsight circle on the weapon stand virtually motionless on the target. Even if you move your head so the frontsight move from one side of the diopterhole to the other , the frontsight will seems to stand still in relation to the target. A peepsight can therefore not be called diopter , although it often is .
Dioptersights has the advantage that the shooter will not have to concentrate on the rear sight and thus only have two things to deal with: the frontsight and the target. The eye need not be centered in the middle of the line of sight to achieve accuracy and dioptersights provides increased in depth sharpness , which in turn facilitates aiming . Dioptersights and peepsights requires that the shooter places the eye close to the sight, while an open sight must be placed at least 30 cm away to make the sights appear clear. " "


The fact is, that if you have a larger hole in the rear sight than 1.2 mm you have in reality not a dioptersight, but a peepsight. ( That's why many grown shooters are struggling with the sights on the G3 weapon. The hole is too big to get the dioptereffect , and the post is unclear)
There are quite a few shooters who have contacted me to get shooting glasses. Many have rather than new glasses, been sent home with new knowledge about the proper use of their sights . The “shooting glass cash”, I told them to spend on more ammo from Norma ......

The same Sjöqvist was also keen on getting the line of sight as long as possible , ie the distance between the rear sight and front sight .
The Mauser was difficult , there was not much to do, while the Krag had the Schou sight, that we could adjust backwards. And then came the Hauge sight with its fine tubes.
When the Sauer were introduced, the situation was much better, there were more adjustment possibilities.
Many shooters with "half good " vision that had hung the Krag on the wall, actually began to visit the shooting range again!



So, how good eyesight must one really have to assert oneselves on the range ?

100 % vision, or 6/6 or 1, o is different denominations on top visual acuity . And 100 % corresponds to the bottom line of the old vision boards , as we all have seen at the doctor's office . However, it should be read on 6 meters distance. (But how many doctors' offices is 6 m ?). Most of our top shooters have 100 % visual acuity or better. But fortunately there are exceptions, and I have information that shows that one of the “Kings team” participants in recent years have not more than 80 % visual acuity .
This shooter is handicap conscious and concentrate consistently on the frontsight circle , and let the target be a " fuzzy dot " .


What should I focus on? frontsight or target ?

Gary Lee Anderson ( Olympic champion at 300m in 1964 and 1968 ) once wrote , that he let the focus slip between frontsight and target, and he estimated that he stopped somewhere in the middle .
Some shooters want a clear frontsight , while others want the target crystal clear. When I have shooters in the " optician chair " I listen to what they want and what their "problem" is . There is no defined answer on this matter .


I am a beginner, can I shoot with my ordinary glases ?

This question I get often , and I often answer yes to the question .
If you only shoot in one position it can work out quite well , at least as long as you keep your head in the same position all the time.
It goes without saying that you look pretty skewed through a common spectacle at prone position , and eyeglass strength is also slightly changed because of that. But changing the head angle between the strings of fire or changing the firing position , the optics in glasses changes and you can easily get a different point of impact. You shoot high , low, crooked groups as a result.
Many people today use lenses mounted on the sights , and then the lens is always perpendicular to the line of sight. If you are farsighted and do not vary the distance from the eye to the rear sight in the different positions, it can be an alternative to ordinary shooting glasses. If you are nearsighted , you get a negative effect with this device . Then it will be like looking through a telescope the wrong way. You get a reduction of the image , the more negative the smaller image. If you are however positive and farsighted you get a pure “scope” effect , with magnification as a result. Are you really overly farsighted , plus 4 or more you get a really big target and frontsight . Then " Adlerauge "is just as a toy in comparision ........

Shooters who are nearsighted must, because of the aforementioned reasons, get the lens as close to the eye as possible. The spectacle lens to norwegian woman champion, Mette Finnestad is as close as I can manage without her winking in the backside of the glass. ( can not get the female shooters to trim their eyelashes ....) But even with these optimal glasses are Mette’s sight- image slightly smaller than one shooting without glasses.
If Mette is to avoid this little flaw , there are two options.
1: Contact Lenses .
2: Refractive Surgery .


Several of our best biathlon athletes, spearheaded by Ole Einar Bjoerndalen and Tora Berger shoot with lenses.
They have no choice due to dew , snot , sweat , tears , rain and snow.
But they shoot fast, and that's what you have to do if you’re shooting with lenses. Aiming much over 2 seconds gives an image that " slips out " and you have to start over again after some blinking . I have a rule saying that 2 of 20 make it work with lenses for normal range target shooting .
Lens wearers who shoot on the range, often end up with a shooting glass in front of the aiming eye , and so retains the lens on the other eye.



Refractive surgery –Laser surgery ?

I took a laser treatment 4 years ago . I could not wear contact lenses , and half the fall is spent in the woods with my dogs . I was previously myopic minus five and was totally dependent on glasses. Now I hunt and shoot without glasses.
Am I happy with the work that Memira performed ? As an optician I knew that night vision would be impaired , and hunting in the "blue hour " is not like before . But in the remaining 23 hours of the day , I'm happy.
As an optician , a former active 4[SUP]th[/SUP] class shooter and instructor , I often get questions about sights. What kind of circle insert I recommend , size, thickness , plastic inserts etc.
To start with the rear sight. I recommend a variable aperture. Remember that light , both indoors and outdoors vary widely. Therefore, before the testshots , turn the aperture down until it starts to get dark , and then up again untill the light is ok. At the same time you make sure to check the front sight insert and the target, to check the contrast of the image in the sights.
Many people have much greater distance from the eye to the rear sight while shooting standing , than they have at prone . Then they must of course have a smaller hole in the rear sight on the prone position, than the standing. ( There are many who are careless here… )
Size of circle inserts is very individual , but I say again what Oskar Sjöqvist preached to us . Largest possible hole in front and smallest possibly at the rear. 4.2 on the range, and 2.6 in the field was what I used in my " heyday " ...................

Care of aperture is important. Micro dust and dirt easily settles inside the iris aperture, so some real "air" once in a while does not hurt . And then there’s the color filters then. Everyone knows how the sunglasses look like if you haven’t cleaned them in a month's time?



What is important for me that would procure shooting glasses?

Are you nearsighted more than minus one, you need a lens that can be built in close to the eye. Are you farsighted with or without astigmatism you can choose a little more freely , or try the lens mounted on the rear sight. Anyway I always recommend mineral glass on shooting glasses or sight mounted optics . By that I mean lenses in glass material and not plastic glass . This significantly due to durability. In the " climate " we shooters inhabit , you will soon have a micro tear in the plastic glass, and I promise you, you’ll see it ! Glass qualities are many , but with a Super Anti-glare treated " glass lens " for under 100 USD you can get as far as you want ..................



What is important to me that has acquired shooting glasses?

The most important thing is that the glasses are customized so you can use your natural firing position , and not have to move your head in an unnatural position to be able to see through the glass. Then it is important that you see in a straight angle through the glass.
This is a real challenge , especially for those who shoot more than one position. Match shooters have time to adjust their glasses between the strings, We DFS shooters have not.


Adlerauge .

Adlerauge is a magnifying lens mounted in front sight . It provides a larger image in the sight, as both insert and target appears closer. Any previous shooting glass correction is used as before. Adlerauge favors no one, no matter spectacle or vision acuity, and it is a good tool for those who’s vision is a little less than normal. As of today there are only veteran shooters who can use Adlerauge in DFS .


My comments:

DFS = Det frivillige skyttervesen (The volunteer shooters movement).Norwegian equivalent of the FSR.
Schou diopter. From around 1930. The aperture is mounted on a profile that can be adjusted back and forth, so it can be the same distance from the shooters eye in both prone and standing positions.
http://www.digitaltmuseum.no/things/repetergevr-65x55-krag-jrgensen-m1894/FMU/FMU.056340

The Hauge sight for the Krag had long tubes with the aperture. The frontsight tunnel has a flat base, wich makes it easier to keep the rifle straight. The front sight inserts are fitted in a dowtail, parallel with the barrel. The inserts can be moved to the front of rear of the tunnel, according to light conditions.

Sight mounted optics = Monoframe http://www.norma.as/Skytterlag/Sikt...le-Monoframe-Skytterbrille-812291-p0000004239

Adlerauge = german for eagles eye. http://www.kornoptikadlerauge.de/index.php/en/adlerauge-en
 
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