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measuring group size

2K views 11 replies 9 participants last post by  gunplumber 
#1 ·
I have a question about getting an accurate group size. I've always shot 3 shots in a group. but i just seen something that says you should shoot 4 to 5. Is it better to shoot 4 to 5?
 
#2 ·
I don't know that there is a "standard" for how many shots constitute a group. By definition, two or more shots and you technically have a group. I'm of the opinion that the more shots you have in a given group, a more accurate evaluation of the accuracy/consistancy of the shooter, rifle, and ammuntion you'll have..... having said that, five-shot groups suit my needs, but others may prefer more.
 
#4 ·
It all depends on what level of "resolution" you seek. The more shots the better if you have the means to do so. A 5 shot group is typically what is thought of a as measurable group in regards to marksmanship. A 3 shot group is just fine for sighting in your rifle or your average deer hunter; but try to pass off a 3 shot group of 1/2MOA to a competition benchrest shooter and you'll probably meet resistance.
In my case, I usually shot 3 shot groups and call it good, I don't shoot competition and can't "waste" alot of ammo on getting my group size to a gnats behind. Going from 3 to 5 shot groups is a 66% increase in ammo costs, ,so it's about the funds for me.

Hope this doesn't overexplain it; if you can shoot 1/2MOA in a 3 shot group and you're happy with it, I'll buy it for a dollar. ;)
 
#5 · (Edited)
Its about statistics: The more samples you have the higher the probability the gun will perform randomly within those results.

Typically for hunting rifles people use only three shoot groups. For all other rifles and handguns five shot groups is considered adequate to gain enough confidence that any one random shot will fit in the group specs. People who live by statistics will insist more shots are necessary to increase the probability. I use five shot groups on everything. I often shoot ten or more shot groups for my 22LR Target pistols for gross comparison of ammo's.

But you get to choose however you want to do it based on your requirements for the probability risk you can take. The only way to compare between your guns and those of others is with the use of the same groups size and the same range.

Typically rifles are shot at 100 yds, centerfire handguns at 25 yds, and target handguns at 50 feet (because most indoor ranges are 50 feet).

LDBennett
 
G
#6 ·
I have always shot 5 shot groups mainly because that was how I was taught. Another reason for me is that I HATE an uneven number of fire shells in my ammo box. I have a touch of OCD in some respects. I will shoot 5 shots because that is the number of shells in one row of my ammo box. I can't stand to have a row with 2 loaded rounds in it. Just drives my buggy.

Also if you don't want to have do any cyphering just down load On Target http://www.6mmbr.com/ontargetsoftware.html

It does all the hard work for you.
 
#7 ·
The convention is a 5 shot group for the reasons indicated. Actually, I get great results with my one shot groups.

I think the idea is that 5 shots will rule out fluke groups that don't really show much about the accuracy of the rifle under practical conditions. It is also likely that 5 was chosen because that is the number of rounds in the magazine of the bolt action military rifles (M1903 and M1917) used in target shooting in the time when so much marksmanship tradition was established (1920's through the 1940's).

Jim
 
#10 ·
On rifle builds, the accuracy here is 3 shots at 100 under 1in. 99% of these guns are for hunting and conditions change so fast (bbl heat, wind etc) that it would be almost impossible to guarantee better in field conditions. Rifles are proven on the bench with one type or another factory ammo but how you manage it in the field is up to you. I tell my hunters if they can't manage it with three shots, they need to keep to the house...........
 
#11 ·
Remember science says that the probability that any one shot will fall within a group spec is a function of the measurement of the group size specification. So the more shots in the group testing group the greater the probability the next shot will also fall within that spec. Said another way, sample size increases probability. Most statisticians will frown at 3 shot groups as a measure of accuracy. Five shot groups are marginal and ten shot groups starts to be meaningful.

While a hunter probably will never need more than three shots to take game that has nothing to do with the probability that any subsequent shot will hit where the first one did. To determine real statistically correct groups size specs you most certainly need more than three shot groups. Five shot groups are better and more than that than better yet.

But the industry standard seems to be that hunting guns/calibers get three shot groups comparison where as others get five shot group comparison. I have kept data on most all of my guns and I have seen spectacular three shot numbers that fall apart for five shot groups. Three shot group specs are much easier for manufactures to maintain with their production process and a lot less expensive.

LDBennett
 
#12 · (Edited)
I have a man that uses a 8in paper plate as a target at 100 for his BlkPwdr gun. If he can hit it, he's ready for the field and he kills every year. If your intention or requirements are 10 shots per string, then use that as a guage. Only you are able to determine what is acceptable for your own needs. A Rem rep told me that if your gun shoots 3 shots within 4in at 100, you do not have a gun problem. I have other ideas about it. I shoot 1 shot before season to see that the old girl is still on and I go hunting. As most all my customers are hunters, well.....you can see where this is going. My personal requirement for my hunting arms is 3 shots in .075 or less at 100 yds. If it don't do that good, I sell it or commence working on it till it will (for cntr fire guns).
 
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