Sighting Errors - It's not the gun...

[LRaccuracy]

At some point in our shooting experience most everyone learns that one-minute of angle is equal to 1.0471 inches at 100 yards. Most of us ball park this figure to “about an inch” at 100 yards. That always worked for me. I’m happy with that. I’m pretty sure that I will not be able to shoot as well as my firearms are capable of shooting anyway.

I ran some numbers the other day concerning human sighting errors. Actually just some simple calculations in geometry told me why I don’t hit the X every time I pull the trigger.

Here’s what I found. With a sight radius of X inches and with a sighting error of .001” (one thousandths of an inch) of elevation, the bullet will impact by N inches off of your intended target area.

Sight Radius ---------------------- Elevation change ---------- Impact change at 100 yards

13" ---------------------------------.001” ------------------------ .2769”
14" ---------------------------------.001” ------------------------ .2571”
15" ---------------------------------.001” ------------------------ .2400”
16" ---------------------------------.001” ------------------------ .2250”
17" ---------------------------------.001” ------------------------ .2118”
18" ---------------------------------.001” ------------------------ .2000”

This may not surprise you but it surprised me. That means if I have a rifle with a sight radius of 18 inches and I am shooting at a target 100 yards away AND my sight picture is off by two thousandths of an inch, I miss my target by .4 inches. The sighting error is not even the width of a human hair.

Okay now everyone can tell me that they knew this. I must have been living with my head in the sand.

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The below was added after posting the original thread:


I did the calculation on a 4" sight radius at 25 yards and this will floor you.

With only .01" (one-hundredth of an inch) sighting error at 75 feet, the impact of the bullet will change by a whopping 2.25".


Sight Radius ----------------- Elevation change ---------- Impact change at 25 yards

4" --------------------------------- .01” ------------------------ 2.25”

 

[Mr.510]

This is why all my rifles have scopes!

 

[Sheldon]

Makes you appreciate more what it takes to shoot iron sights consistantly.

 

[JohnKSa]

Run some of those numbers for pistol-length sight radii and 25yds. That's another eye-opener.

If you're shooting a compact pistol with a 4" sight radius at 25yds a hundredth of an inch sighting error (about the thickness of 6 pages of a typical glossy magazine) will move the POI more than 2 inches.

 

[Impureclient]

So basically the guys saying they can shoot their $3000 1911s at 25 yds in 1" groups or less
are able to hold the gun in their hands so still that it moves no more than 3 pages of paper?
Is that possible without using a laser on the target for guidance?

 

[General Geoff]

Most guys who are able to do that, can only do it consistently from a bench, holding the pistol with their hands on a stable surface. Shooting freehand, it would be far more difficult to do so.

 

[WinchesterAA]

I can do that with my officer's model all day long by myself. Still working on mitigating the constraints spectators apply on a situation.

 

[NukemJim]

Is that possible without using a laser on the target for guidance

IMHO and limited experience LASERs will not help to obtain the accuracy we are talking about here.

I have 3 LASER equiped handguns (long story) and only use them when teaching newbies and by request for my young nephews/nieces. And occasionly just to pop the hot air balloon of range commandos
(They get the LASER equipped handgun I get the iron sighted handgun, haven't loss yet )

I do not know but from my limited understanding the situation is similar in longarms.

NukemJim

 

[LRaccuracy]

JohnKSa,

I did do the calculation on a 4" sight radius at 25 yards and this will floor you.

With only .01" (one-hundredth of an inch) sighting error at 75 feet, the impact of the bullet will change by a whopping 2.25".


Sight Radius ----------------- Elevation change ---------- Impact change at 25 yards

4" --------------------------------- .01” ------------------------ 2.25”

 

[NoAlibi]

Dang!

LRaccuracy
Okay now everyone can tell me that they knew this. I must have been living with my head in the sand.

I've had a Ransom Rest since 1980 and one VERY accurate pistol and I've known since then it was "not the gun."

But I had no idea that sighting errors that were so minute could cause that much of a difference! I was going to thank you for the heads-up until I realized that I'll be thinking of that every time I pull the trigger!

WinchesterAA
I can do that with my officer's model all day long by myself. Still working on mitigating the constraints spectators apply on a situation.

I've noticed the same phenomenon when shooting my NAA mini!

 

[Japle]

In 40 years of serious pistol competition, I've only been able to do this a couple of dozen times.


Note that the target above was shot over 10 years ago.
Since then I've had a few more good days:



Learn the basics and practice them. And remember, it's not the gun!

 

[LRaccuracy]

I'll never be National Match Championship material, but I do win a match now and then locally. With that being said, I think I know what it takes to shoot targets like the one's displayed above, and there is no way I can do that on a consistent basis.

Thanks to everyone so far for you comment and thanks for posting the pictures.

Becoming more intrigued with the mechanics of shooting and of course the external ballistics, drove me to look at some things I never considered. I must have to much time on my hands.

Thanks, LRaccuracy

 

[JohnKSa]

Is that possible without using a laser on the target for guidance?

I really don't think that the laser will help that much unless the shooter has vision issues, the sights aren't visible or are poorly designed or the shooter simply doesn't know how to use the sights.

Either you can hold the handgun steady or you can't. It's my opinion that most of the error on target is not due to sighting errors but is due to the shooter moving the firearm during the act of pulling the trigger. The human eye is amazingly good at lining up sights and targets.

 

[stillaftermath]

Good god. I've got a medical condition - benign essential tremor - that essentially makes me shake like a damn leaf all the time. The "perfect sight picture" exists in my eyes for thousands of a second; I basically "vibrate" down on the thing and pull the trigger when it feels right.

I can't believe I'm staying in the black let alone bullseye, after hearing this bit! I average 3-4" groups, with a flyer or two, with handguns at 25 yards; but hell, if you guys could see the sight picture I work with because of my hands you'd probably be surprised I hit paper.

(P.S. - There is medication I could take for benign essential tremor, unfortunately the most common are anti-anxiety meds that would be inappropriate to take while handling firearms. Besides, I figure if I can't shoot au naturel, I can't shoot at all. 100% of my shooting is stress-fire!

... the other thing that eliminates it? Alcohol. After a drink or two my hands are steady as a rock. Again, however, ranges tend to frown... ;P )

 

[TimRB]

Here's an experiment you can perform to see what your sighting error (including your eyesight) really is...

You will need an assistant. I'll presume you are doing this with a rifle.

First, point the rifle at an immovable blank piece of paper 20-30 feet away, and lock it into a vise or some other device that holds it steady. You need to rig it so the rifle absolutely, positively cannot be moved. Make sure you can get your face up to the stock as if you were shooting.

Remove the bolt from the rifle and UPS it across the country. Bury all your ammo. Make certain that the rifle absolutely, positively, cannot be fired. Send away all spectators so only you and your assistant are present and there are no distractions.

Make a round aiming black of the appropriate size (do the math) on a separate blank piece of paper. Mark dead center of the aiming black.

While you hold your face up to the rifle looking through the sights, have your assistant move the aiming black around the blank piece of paper until you think it is lined up perfectly (whatever you think "perfectly" means). When it is perfect, have your assistant make a pin prick through the aiming black dead center so that there is a tiny hole in the blank piece of paper.

Do this several times and measure the group size (do the math). Make sure your assistant moves the aiming black completely away from the blank piece of paper between "shots". Try it with different stock holds, face positions, etc. This will tell you the very best you can expect if you are shooting a perfect rifle with perfect ammo.

Tim

 

[NoAlibi]

TimRB
Make a round aiming black of the appropriate size (do the math) on a separate blank piece of paper.

This sounds like an interesting experiment and I'm going to try it.

The only thing is that I'm not quite sure what you mean by a round aiming black of the appropriate size.

Would you mind elaborating on that? Thanks -- NoAlibi

 

[TimRB]

"The only thing is that I'm not quite sure what you mean by a round aiming black of the appropriate size."

Well, for example, the aiming black on the SR target (shot at 200 yards) is about 13 inches in diameter. If I wanted to make a target that had the same look at 100 yards, I would make the aiming black 6.5 inches. (3.25 inches at 50 yards, etc.).

Or, for the purposes of this experiment, you could make several targets of different sizes and pick the one you like best.

Tim

 

[NoAlibi]

Tim - Got it - Thanks!

 

[Howard Roark]

These are very good observations on the subject. If you want to delve into dark magic check out the following.

There is another phenomenon at work with aperture sights called parallax shift. In the use of the common aperture sight on rifles in precision target shooting, common wisdom emphasizes the necessity for the shooter to carefully maintain his eye position so the tip of the front sight post appears centered within the circular field of view of the rear sight aperture. Otherwise, goes the wisdom, parallax shift will occur, which will disrupt the accuracy of the shooter’s aim.

In reality this does not occur. Here are two articles with pictures and live fire to explain this phenomenon:

http://doug.kerr.home.att.net/pumpkin/Aperture_Sight.pdf

http://doug.kerr.home.att.net/pumpkin/Aperture_Sight_Demo.pdf

 

[longdayjake]

So basically the guys saying they can shoot their $3000 1911s at 25 yds in 1" groups or less
are able to hold the gun in their hands so still that it moves no more than 3 pages of paper?
Is that possible without using a laser on the target for guidance?

I personally watched someone do it offhand and it really made me sad becaue my groups are more like 1 foot at 25 yards.

 

[22-rimfire]

LR, good post and it helps to be reminded just how difficult it is to shoot small groups. Scopes help. I once made the comment on one of the forums that I could consistantly make 1" groups at 100 yds with my Remington 541-S (22LR). Boy, did I get challenged quick and I mean quick about my assertion. I can do that on a good day. So, I then went out and shot and believe me it is very hard to do 1" groups at 100 yds with a 22LR consistantly. It is why I shoot at 50 and 25 yds mostly. There are so many factors that affect group size that for me that it is the exception rather than the rule in terms of shooting. S. Boelter's book uses average group size to test a particular ammo. The groups always seemed large to me.... I can do better than that... yeah, I can, but not on the average.

Shooting a handgun well is very difficult. You can hit a man sized target pretty easily. But shooting those 2" or less groups takes a lot of practice. In terms of self defense and shooting "straight", 6"-8" groups are fine. That puts self defense into perspective and why a firearm is a good instrument for self defense even if you only practice occasionally. Of course, unders stress, you probably will do worse. I'll deal with that if it ever happens, I guess.

 

[5knives]

Ummm ...

You don't hold the handgun rock steady ... you can't.

(though a couple of years of practice , say 2 hours a day. with a pair of sand filled combat boots slung over your shooting wrist, will help build the muscles that can let you get closer to rock steady.)

But what really helps is the basic marksman advice, you only take up the trigger when the sights are on, then you wait until they're on again and take up a little more. Eventually there's a 'BANG" and if you did it right the bullet goes where you wanted it to.

Scopes and lasers can make everything worse by showing the shooter just how shaky he/she is. 'Till they get used to them of course.

And FWIW, a 12' group at 25 yards is quite acceptable for SD. Means every shot was within 6 inches of the intended aiming point. I think we all fall into the trap of demanding pin point accuraccy from all our firearms, while completely missing the fact that the real world use of that firearm rarely (if ever) gives us the opportunity to use that accuraccy to any significant degree.

Least that's the way it was taught 50 some years ago.

Target grade accuraccy with a handgun is an extremely difficult sport to get proficient at. That's because unlike most other sports the regular practice of the sport does NOT build the muscles, breathing habits, and endurance necessary to excel at the sport. At least not in the span of a normal human lifetime. Those things have to come from elsewhere, cross training is the popular phrase today.

JMHO, nothing to get excited about, of course YMMV!

Regards,

 

[LRaccuracy]

22,

I have always strived for that perfect group after my father stopped me from shooting bottles and cans. I found that shooting paper targets gave target shooting meaning and something to measure your skills.

I really was encouraged to post this thread because I could not find this information anywhere on the web. I may make up a chart for handguns and rifles and post it someplace. Most everyone understands MOA but some people do not understand how steady you have to hold your firearm when aiming even if they can do it. Others can't understand why the can't hold a tight group like the person standing next to them at the range.

Anyway it's good information (I thought) and it is interesting to some.

BTW I did use some of the information I collected with the 22 LR @ 100 yds. -- One Hole Obsession post. My groups are getting tighter and I did win the match this past Sunday. We fired 30 rounds at 100 yards and I scored 297 out of 300. I dropped 3 rounds in the 9 ring and I had 16 X's fired on a MR-31 target. I have shot scores like this before, but never 16 X's.

 

[LRaccuracy]

5Knives,

I agree the boots do help. I learned to shoot in the Marine Corps, and some of the training we received I still use today.


Semper Fi....

 

[Maxw]

Olympic pistol shooters in free pistol (50 M) and rapid fire (25M) perform like that at the world level. The same goes for bullseye (25 & 50 yds) and international standard pistol (25M) on slow fire targets for all stages of slow, timed & rapid.