Definition of Grouping?

J

Joseph

New member
I've heard a variety of definitions on grouping, but I'm sure there is a common one.

For example, is a 5" grouping where:

A. All shots fall within a 5" diameter, or
B. The 5" is a radius from the centermost bullet hole. This would be an effective 10" diameter grouping.

I have always felt A is correct, but since I've never shot competitively, I'm not positive.

Next, when firing at a target at 25 yards (75 feet), my front sight (regardless of gun, SIG P232, P239 or USP9) covers much more than 5 inches of a target. As far as I can see, I'm guessing where the round will go in the large area covered by the sight.

When I hear people shooting 1-2" groupings at 25 yards, how do they sight?

Thoughts?
 
Group size is measured from center to center on the extreme spread. Find the two rounds that are farthest apart and measure from the center of one to the center of the other.

The best shooters can shoot small groups either holding at 6 o'clock or center of mass. The x-ring has been shot out of a lot of B-27 targets at 25 yards holding center of mass. You just have to remember to hold on the center of the big ragged hole as it grows.

As any of the top shooters can tell you, given the physical ability and good equipment, the game of shooting those little tiny groups becomes a mental one.

Had to edit. By the way, very few people can consistently shoot a 1 to 1 1/2 inch group standing without support at 25 yards, especially with iron sights. The truth is, such an individual would be Olympic class and rare indeed. Shooting an inch and a half group off of a bench with optical sights is a different story.

[This message has been edited by Ankeny (edited February 14, 2000).]
 
The way to measure group size is to measure the distance from the outside of the furtherest holes and subtract the bullet diameter. EX. for .223 (.224) you subtract .224" from the aforementioned measurement.
 
Thanks, guys.

What would be considered a "realistic" goal of groupings shooting without support with iron sights at 25 yards?

A follow up: When one hears about placing 5 rounds in 1.5", how many rounds does one get to fire. Is it 5 out of 5, or out of 8?

Thanks again.
Roon
 
I've got to mention this. Gun writers (some) have a whole different version of "group size" and occasionally you'll see the infamous 2" snubby .38 shooting 3" groups at 25 yds. I'm not saying its impossible, but.....
 
IMHO you have shot a 3 inch group IF ALL YOUR SHOTS fall inside a 3 inch circle. None of this center to center nonsense. Nicking the outside edge of the ten ring and calling it a bullseye is equally reprehensible. And damn near anyone who says they can off hand a 2 inch group at 25 yards with iron sites on a handgun.. well.. it is indeed a rare thing. Now from a bench or hard rest with a target pistol.. sure thats possible.

Its like when we score 100 yard rifle targets when I say hey I shot a dime sized group of 3 rounds (and folks flyers COUNT) that dosen't mean a dime touches all three holes.. that means a dime COVERS all three holes.

Now how they score it in IDPA, or IPSC may differ.. I'm just saying what I think.

Dr.Rob
 
Humble opinions not withstanding, the standard way of measuring groups is center to center of the holes that are farthest apart. This is why we see in benchrest shooting the seemingly impossible condition of a .30 rifle shooting .20 inch groups.

Also note that group size is only one factor of accuracy. A .5 inch group at 100 yards that is four feet from center bull is a great group, but there is something wrong with the accuracy of the rifle, nonetheless.

Jim
 
Dr.Rob, I think you are arguing against a "standard". As with most things that are measured, there has to be a standard method of measuring. The accepted standard method is to measure from center to center of the holes. Since guessing where the center is is difficult, there are several ways to accomplish this, measure from the outside of one hole to the inside of the furthest hole or measure from the outside of both holes and subtract one caliber.

I think you are being too hard on yourself if you measure groups your way. If a bullet hole touches a ring it takes the score of the touched ring. If we had to fire completely inside a ring to count it, there would be very few X's in all competitions and the "standardized" scores would be lower. That isn't necessarily bad, because we would be used to the range of scores that standard method would yield and an X would really mean a true X. But, that isn't the current standard.
 
Well mal.. are you saying I shoot BETTER than i thought? (does that mean my lowly Savage rifle can shoot .3 moa??)

All seriousness aside guys.. please remember at times I'm just a guy who grew up zapping pop cans and bottle caps. If the can didn't move it was a miss. I'm a good shot on the bench and in the field I can call my shots out to about 300 yards... beyond that well.. i need more practice/instruction. The funny thing is almost ALL of my shooting past 300 yards ahas been at live game.. not at targets.

I often note that the gun rag types 'discount" flyers when they are evlauating a bullet or gun or whatever.. if you want to see how the GUN shoots, lock it down in a ransom rest.. when you are seeing how YOU shoot.. flyers count. Sometimes you flinch.. sometimes you oversqueeze, etc.

Anyway.. when you see me say hey I can shoot a fist sized group with my 380 at 20 feet by point shooting over the front sight.. I don't expect 'target" accuracy.. so I say things like 'fist sized or softball sized" its just an aproximation.

I do take 25 yard off hand claims of 2 inch groups with a large grain of salt.. i know there are guys that can do it...but they are indeed rare.

Anyway..

I'll start measuring center to center if you like..

but don't be suprised if my groups shrink and my scores go higher. ;)

Dr.Rob
 
Yes, Doc, you are better than you thought!

I whole heartedly agree with you on "flyers". To my mind, there is only one circumstance where flyers should be allowed. That is when you are attempting to check the accuracy of a pistol/rifle from a bench rest. If you are sure that the shot you just fired will be off due to a flinch, etc., then you can discard it. For most other groups you are checking your own accuracy and every shot counts.
 
A "flyer" might be due to ammo, shooter, or gun. In competition, it doesn't matter--it counts.

In testing a gun for accuracy--and best done from a rest, to my mind--a "called flyer" is known by the shooter to be his own fault and not that of gun or ammo.

If you're testing, and you don't feel you were ever off on your sight picture, yet every group has a flyer, that flyer determines the group size for accuracy assessment. Which is why it pays to try different ammo--sometimes it ain't the gun nor the shooter.

:-), Art
 
Joseph, I thought you were a political junkie. I didn't know you were into shooting too! (g)

I've always been told that shots were measured center to center using the widest spread as the measure of the group. Hope this is correct.

Dick
 
Dick,

I couldn't be a political junkie around here without the ability to defend myself!! :D :D :D

By the way, I will only count something in any ring if at least half of the round falls within it. It may not be the way the officials count, but it only seems fair to me!

OK guys, so you count your groupings for all the rounds you shoot *for the book*, not counting flyers if that be your discretion, correct??

By the way, if any of ya'll want my Word document for a printable 8x10 target of 8 through X-ring, just drop a note.

Roon

[This message has been edited by Joseph (edited February 15, 2000).]
 
I have often considered this question myself because of a math background and I have found there is 2 reasonable (?) ways of measuring the groups.

One way is to measure the maximum spread of group or from maximum outside edges of the bullet holes and subtract one caliber for center to center spread. This is the easy way of measuring a spread.

The more diffucult and scientifically more accurate would be to figure the center of mass of the group and then measure the inches of deviation from the center point of the group. To do this you would draw intersecting lines between many of the extreme shots and find the relative center point of the group. Now measure the distance from the center to each bullet hole, sum the number and divide by the total number of holes.

The advantage of the second technique is it is a truer (?) measure of what a gun shooter interface will do, ie: it takes into account the flubbed shots, the first round wild hits etc and gives an accurate assessment of the whole shooter system. The problem of the second technique is it is a pain to do.

Now if you really want to kick the fat in the fire, why not ask how many rounds it takes to shoot a "representative" group? I contend that it takes 10 or so shots per group to get a good statistical sampling. I find it interesting when I read about 3 shot rifle groups. When I test reloads on my M1A's I usually shoot 20 rnd groups to get a feel for the accuracy. On my pistols I usually shoot between 10 and 14 rnds per group if I am really trying to test the accuracy of what I can do.

Alternative theories?
 
Joseph:

What is a realistic goal at 25 yards? I guess that depends on what you are shooting and how you shoot it. Shooters and their groups are inversely proportional to fishermen and their fish. The groups get smaller every time they tell the story. It isn’t that shooters are liars, they just have poor memories and can’t measure.

You asked a legitimate question and you deserve an answer. With my better “stock” handguns, I have no problem shooting groups consistently day in and day out at 25 yards, standing without support with iron sights that hover right around the 4 inch mark. My heavily customized target guns do much better. I am 44 years old and I started competing while in junior high school. My last classification for PPC was Grand Master and I shot Master Class in Action Pistol. Yes, lots of men, women, and kids shoot better than I do. Perhaps some of them are posting on TFL. Still, I am very skeptical of those who would have me believe they shoot groups half that size with stock guns on a daily basis.

When speaking of accuracy, the Bullseye (2700) shooters are the guys to beat. They are incredible shots and unless their pistols are capable of less than 2.5 inch groups at 50 yards, they will never get to the top of the heap. I don’t remember his name, but there is a regular here on TFL who shoots Distinguished and he would be a good source to go to for hints on accuracy.

Try this, get a 25-yard timed fire pistol target. Shoot ten rounds in 20 seconds with your favorite handgun then score the target. This is arguably the easiest stage of Bullseye shooting and the better shooters will routinely clean the stage. Anything above 90 percent is very good for most shooters.

If you don't want to get that formal, then I would guess anything less than 3 inches (stock gun) at 25 yards would be considered pretty good. Then again, when the timer comes out and you have multiple targets the whole game changes. Does that help?
 
Peter ... Since you asked, wouldn't it be more fair to take the standard deviation of your distances from the center of mass? Instead of taking the sum of the distances, take the square root of the sum of the squares of the distances and divide that by the number of shots. Multiply that number by six and you get the diameter of a circle that 99.7% of your shots will fall into ... statistically speaking, of course. Personally I like the center-to-center of the farthest 2 holes method ... all you need is a ruler.
saands
 
Ankeny,

Re: "Try this, get a 25-yard timed fire pistol target. Shoot ten rounds in 20 seconds with your favorite handgun then score the target. This is arguably the easiest stage of Bullseye shooting and the better shooters will routinely clean the stage. Anything above 90 percent is very good for most shooters."

Where does the figure 90 percent come from? How is it calculated or measured?
 
Ankeny,

I believe I'm doing what you suggest now, if I understand you correctly.

I use a bullseye target with graduated rings from seven through ten, plus an X which counts as 10, which I believe is the target you are talking about (the nine-ring has a diameter of a skosh over 5.5"). If I shoot 10 rounds, and end up with a total score of 90, I assume I am shooting your 90%, or an average of 9 points for every round.

Shooting 30 rounds in slow fire single action at 21 feet, my best is 9.8 for my USP9 shooting Wolf, and 9.7 for my P239 .357 SIG (Lawman). This discrepancy makes sense to me since the USP has a longer barrel. My P232 drops to 9.44 (Glaser).

When I go to 50 feet, I get 8.1 for the USP (Wolf) and 6.43 for the P232 (American Eagle).

75 feet gives me 6.37 for the USP (Wolf) and 3.8 for the P232 (American Eagle).

(I've just started keeping these target scores like this, so nothing on the P239 yet at over 21 feet.)

I obviously have a big drop for the 50 and 75 feet, with stock guns and target ammo. I don't expect the P232 to be very accurate at 50 or 75 feet. I do think I should get improvement out of the USP9.

I will now start another data field for groupings, based on this info.

Thanks all very much for your insights.

By the way, if any of you want the Excel spreadsheet I use for inventory, target data and shot log, drop me a line. I've finally got the kinks out of it.

Roon
 
Ankeny,

Just FYI: the timed fire strings in an NRA Conventional Pistol (Bullseye) match are 5 rounds (not 10) in 20 seconds, two strings per target. The shooter fires one handed from an unsupported standing position and unlike a UIT (International) competitor can start the string with the pistol pointed at the target.

Anyone who wants to try shooting timed fire should be sure to use the right target. There are different targets for matches held at different distances (50 feet and 25 yards) and the targets used for timed and rapid fire have more generous scoring rings than those used for slow fire.
 
I've gone to this site: http://www.bullseyepistol.com/ which has loads of good info.

It appears that the target I've been using, listed above, is for 50 feet. This would account somewhat for my poorer performance at 75 feet.

However, true bullseye, as listed in the site above, calls for one-handed shooting. I do all of mine with two hands. A major advantage!

[This message has been edited by Joseph (edited February 16, 2000).]
 
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