Sight Radius vs Accuracy?

[HGM22]

I am wondering if anyone has any information on the ties between increasing sight radius and accuracy? Something similar to the Ballistics by the Inch would be great, but difficult to accomplish, so not sure its out there. I'm really wondering if there are tiers of sight radii (an exponential relationship) or if its more linear.

For example, are 20'' barreled AR15s markedly more accurate than 16'' AR15s, but the difference between 11.5'' and 16'' AR15s is not nearly as much?

Or for handguns, are 4'' revolvers way more accurate than 2'' revolvers, but the 6'' gun is only slightly more accurate than the 4'' (tiered)? Or is the increase in accuracy from 2'' to 4'' equal to the increase from 4'' to 6'' (linear)?

Edit: I get that this is a subjective question and will differ person to person.

 

[M-Cameron]

a longer sight radius doesnt inherently make a gun more accurate.....

but what it does do is allow you to see smaller discrepancies in sight alignment much better......which can lead to more accuracy.

 

[MrBorland]

The shorter the barrel is to start with, the more a longer barrel helps. Going from a 11.5" to a 16" barrel gives you a 39% (=4.5/11.5) increase, whereas 16" to 20" only gives you a 25% (=4/16) increase in sight radius.

Likewise a 4" barrel gives you a 100% increase over a 2" barrel, whereas going to 6" from 4", only increases the sight radius 50%.

Whether any of this helps your shooting is up to you.

 

[Sheepdog1968]

Ballon Goes Up posdcaster (forget his name) has a website. He shot glock 26, 19, 17 in which he had the front sight not centered (off to one side in the rear sight). It was a measurable difference. All other things being equal, have a longer sight radius will aid group size.

 

[9mmepiphany]

I am wondering if anyone has any information on the ties between increasing sight radius and accuracy?

What make you think there is any relationship at all.

Increasing the sight radius of a handgun, doesn't make it more accurate. All it does is make it easier for the shooter to detect smaller errors in alignment between the sights.

 

[grter]

Because of the way humans perceive things visually a longer sight radius does help improve accuracy and in most cases immensly.

A longer barrel is better with 5.56 and .223 calibers period despite what some would be commandos may claim. The round works significantly better out of a longer barrel. That is just a plain fact of physics.

 

[HGM22]

I'm aware that longer sight radius doesn't make a gun more accurate inherently; I meant "accuracy" from a practical shooting point of view.

Same with barrel lengths; when I mention barrel lengths I mean the increased sight radius, not the barrel itself.

 

[General Geoff]

Longer sight radius improves precision, not necessarily accuracy.

 

[rcmodel]

When I was 26 years old, I could shoot a 7 1/2" Model 41 S&W way better then the 5" barrel.

Now at 71, I can't shoot the longer barrel nearly as well as the shorter barrel.

Eyes is the key!!

rc

 

[Deus Machina]

It's tough to measure that sort of thing because it's an aid to the shooter, not the weapon.
For purely numerical statistics, hit up a trigonometry book. I'd help there but I failed trig.

 

[TruthTellers]

A longer sight radius just makes it easier to hit what you're shooting at. Accuracy depends on a number of factors, but having a longer sight radius is one of those factors that aids in increasing the potential accuracy. That is, as rcmodel has said here, so long as you can see the front sight. You can have a barrel with a 20 foot sight radius and still be unable to hit your target because that front sight is so far out there you will probably have trouble seeing it.

 

[Delmar]

I can shoot my 3.5 inch Officers Model as accurately as my 5 inch Government Model, but I have to concentrate a lot more in order to get the same groups. That all falls apart at 50 yards because of my eyes, not the firearm.

 

[Warp]

What make you think there is any relationship at all.

Increasing the sight radius of a handgun, doesn't make it more accurate. All it does is make it easier for the shooter to detect smaller errors in alignment between the sights.

Which is why people tend to be more accurate with a longer sight radius.

In actual shooting there is definitely a relationship between sight radius and a person's accuracy with that firearm. I doubt this can really be quantified though.

 

[USAF_Vet]

I recently put a 15" fore end on my AR, and with a clamp on front site, I noticed a difference in my own shooting. The additional 6" or so of added sight radius made my shooting more precise.

Maybe it's circumstantial, maybe I had better breath control, maybe it was the overall lighter weight and better balance of the gun, the different rate of twist, better quality ammunition, it could have been a number of factors. But I noticed an improvement in my shooting. At the time, I chocked it up to the increased radius.

To be a little more empirical in gathering evidence, I would put everything back the way it was and just shoot with the different sight radius, but I sold that barrel, so too much changed to give an honest answer. Next time I'm at the range, I'll play around with different front sight positions and check for accuracy/ precision variances.

 

[Jim Watson]

You can do the trigonometry, you can apply Internet Expertise on the definition of "accuracy" like you so frequently explain the difference between "clip" and "magazine", or you can resort to empiricism. See what works.

If you had a lot of time and a bit of money to put into it, you could put multiple sight bases on a known accurate gun and shoot it to test the effect of iron sight radius.

You can look at history. Iron sight target shooters have always sought the longest sight radius. Go back to Creedmoor days and look at the rifles with 34" barrels and a rear sight on the heel of the buttstock being shot from the supine position. There was a Ross bolt action set up that way many years later, too.
A modern Palma shooter will have a 32" barrel for the slight added velocity and significant added sight radius.

If you are shooting a rifle or pistol offhand, then you have to start compromising on sight radius to get a balance you can hold steady. And may even accept a shorter sight radius still for clearer focus or just to reduce the psychological effect of sight wobble. But it still comes into play to the point that it appears in rule books.
Do you know why the S&W .357 Magnum was originally available with an 8.75" barrel? Because that gave the maximum rule book sight radius of 10".
Do you know why they soon reduced that to 8.375"? Because they realized there was also a rule limiting single shot barrel length to 10" and that applied to barrel + cylinder length for a revolver.

In the last years before optical sights took over NRA Conventional shooting, there were several gunsmiths (and the S&W factory) making front sight extensions to give a long sight radius with a short barrel balance .

 

[Caliper_Mi]

Getting back to the OP's question, I think the missing part of the equation is what amount of sight mis-alignment will a shooter notice and be able to correct?

Doing some math, it seems like we are able to hold the sights within a very close standard.

For example, with a 20" sight radius (I believe this is the sight radius of a rifle length AR?), a 1 MOA misalignment represents only 0.0058". That's just one side of the error, so to align the sights within 1 MOA of the target means you only have +/-0.0029" of sight alignment tolerance. Of course, to actually shoot a 1 MOA group, a shooter is probably holding closer than that due to ammo and rifle errors, but I'll just ignore those for now for simplicity.

So, let's apply this to other length barrels, using +/- 0.003" sight alignment tolerance, your sights will be within:

28" sight radius: 0.74 MOA
24" sight radius: 0.86 MOA
20" sight radius: 1 MOA
16" sight radius: 1.3 MOA
12" sight radius: 1.7 MOA
8" sight radius: 2.6 MOA
4" sight radius: 5.2 MOA
2" sight radius: 10.3 MOA

I've actually never calculated this before and it's prety interesting. This does show a point where mechanical accuracy really does start to degrade below what one would consider acceptable "practical" accuracy, but it's shorter than I expected. Also, diminishing returns are clearly apparent on the long end, which explains why world militaries never saw accuracy suddenly drop down the tubes when moving from the 30" barrels of the late 19th century to the more handy barrel lengths of the middle 20th century.

I still really like the idea of putting a 24" barrel on an AR and mounting the front sight "dissipator" style out at the muzzle (with a mini gas block further back of course).

 

[lysanderxiii]

Reference point.

A sheet of standard 20 lb bond printer paper is 0.004" thick.....

How well you can detect aiming errors has a lot to do with the relative size of the target/aiming point to the width of the front sight post.