Irritating noober question about sight radius

[brekneb]

Yes I know you all love hearing questions like this one.


Sight radius.... Why is it that a shorter sight radius is less accurate than a long sight radius? I hear it all the time; "yep, shorter sight radius such as on a pistol is far less accurate than a longer sight radius such as on a rifle...."

But why? is my question..... No one ever seems to have an answer as to why, instead I only ever hear about it but not the reason behind it. Anyhoo, can anyone help me out?


I can hear people groaning now......

 

[chris in va]

It's basically the minute of angle aspect. The shorter the sight radius, the less 'precise' your aim will be. The smallest movement will equate to FEET at the target instead of inches.

Try this. Take a pen, point it at something while holding it close to your face. See how much it moves around? At longer distances you could completely miss the target.

Now hold it out in front of you. See the difference?

 

[TAB]

Its all about error, and your abilty to notice said error.

A good way to explain it in every day terms is....

Lets say you need to draw a perfectly strait line 4' long... your choices of strait egdes are a yard sick and a 12" ruler. which of the two would be easier to draw that line with? which one would produce the straiter line?

 

[Splash]

It's only because the further two points are from each other , the easier it is align them. Shorter radius makes it slightly more difficult to keep a weapon in a straight line and/or to align the sights with a distant target.

 

[230RN]

Good question. Not irritating at all. I've been shooting for almost sixty years and still have questions.

Look at it as if it were a long lever system. You've got a long lever consisting of the rear sight, the front sight, and the target.

Now imagine that the front sight is the hinge point (fulcrum) of that long lever and stays put while you move the rear sight.

OK. Now imagine that the front sight (hinge) is halfway down the lever. Any motion of the rear sight will give the same distance of movement at the target. Like a see-saw with two kids on it.

Now imagine the front sight is only a quarter of the way along the lever. Any motion of the rear sight will be "amplified" by three times, since you have 3/4 of the length of the lever in front of the sight, and 1/4 of the lever behind the front sight. (A three-to-one ratio.)

So as the front sight, looking at it as if it were a hinge, moves closer to the rear sight, any "movement" of the rear sight in terms of sighting error is amplified more and more at the target.

So. What happens with short sight radius (front sight close to the rear sight) is that any itty-bitty error in sighting is "amplified" more and more as the sight radius is shortened.

But with a longer sight radius, the same itty-bitty amount of error in sighting will result in less movement (error) at the target.

Just a lever system, is all.

(And looking it as a lever system with the front sight as a stationary fulcrum (hinge point) explains why you have to move the rear sight to the right if the gun is shooting to the left, and vice versa.)

--Terry

 

[sfmittels]

[quote/]Posted by 230RN: Good question. Not irritating at all. I've been shooting for almost sixty years and still have questions.

Look at it as if it were a long lever system. You've got a long lever consisting of the rear sight, the front sight, and the target.[quote/]

Terry - you are my god.

 

[antsi]

A longer sight radius makes a small misalignment of the sights more obvious.

 

[PercyShelley]

A longer sight radius makes a small misalignment of the sights more obvious.

Up to the ability of your eyes to resolve such differences.

My eyes aren't so good, so I don't shoot well with irons of any sight radius.

 

[RyanM]

Practical accuracy only. Misaligning the front and rear sight by 1/16" horizontally on a gun with a 6" sight radius results in missing by 37.5" at 100 yards. With an 18" sight radius instead, the same linear misalignment makes you miss by 12.5" instead.

However, if you're off by a certain number of degrees, you miss by the same amount regardless of sight radius.

 

[ranger335v]

As you will note by the correct info you've gotten, it ain't that a short sight radius is, by itself, a limit to accuracy but it is a limit to our ability to align those sights accurately. That has the same effect but is not technically the same thing as pure accuracy possible from the firearm..

 

[230RN]

Terry - you are my god.

Bless you, my son. You may leave a few shekels in the poor-box by the door.

--Terry

 

[Bwana John]

Anyhoo, can anyone help me out?

OK, try a high school trigonometry class

 

[ADKWOODSMAN]

Antsi+1