Determining firearm group size

[Hannibal]

Just want to pose a couple of simple questions to satisfy my curiosity.

When you shoot a group to determine the firearm's group size, how many shots do you use? 3? 5? 10?

How many errant shots do you discount as ' fliers ' ?

And how many groups do you measure and average to determine the firearm's average group size?

Fired over how many days?

Thank-you in advance for your responses.

[silverjay]

I use five round groups with nothing removed as fliers. I do two groups and usually get bored punching paper.

[williamwaco]

Revolvers 6 ( or however many the cylinder holds )
Pistols 5 ( magazine full is too many)
Hunting rifle 3 ( I have never had a target hang around long enough to shoot five shots at it. )
Target rifle or pistol 10
For Rifles, I use three or more groups to average.
For handguns five or more.

One small group means absolutely nothing.
Here is an actual example from my .38 special testing:
First three 25 yard groups measure 0.78, 1.05, 0.91 -> 10 group average was 1.55"

I do not discount flyers. If I jerked it, I toss the whole target and start over.
If I didn't jerk it, I measure it.

Over how many days? I record them all - forever. Sometimes five groups might take an hour, other times it might take a year.

[waco]

When I work up a load, I start with five shot groups to see if the load even has any potential. If it shows promise, I'll shoot ten shot groups to determine the consistency of the load.

If the barrel is clean, I'll fire at least a few fouling shots. You also want to wait a couple minutes between shots as to not get the barrel too hot.

Depending on how long I'm at the range, a few ten shot groups will tell you how the load works.

As as far as day to day goes, weather can be a big factor there. Sunny and 85 degrees x load shoots just fine. Try it on a 35 degree day and you could very possibly have much different,worse results. Lube being the culprit here.

I'm sure someone with more knowledge on the subject will chime in.
Hope this helped.
waco.

[montana_charlie]

Just want to pose a couple of simple questions to satisfy my curiosity.

When you shoot a group to determine the firearm's group size, how many shots do you use? 3? 5? 10?

Never less than 15 of a particular loading.

How many errant shots do you discount as ' fliers ' ?

None, after the first shot from a clean barrel.

And how many groups do you measure and average to determine the firearm's average group size?

Fired over how many days?

At least four sessions, sometimes fired over a period of a couple of months.

[runfiverun]

to record average group size over time I tape a new target over the old one and shoot through them both.
I have a Remington 700 in 8 mauser that is a pretty solid rifle, it will put everything in a 1-1/2" group at 100 yds.
cold bore to hot, warm and cold weather, sun and rain or snow.
it's a pretty good hunting rifle I think, no fancy tiny little groups just reliable and consistent.

[country gent]

Hunting rifles and handguns I use 5 shot groups, Varmint and true match rifles 10 shots. I normally will test several loads on a given day. Then come back and retest promising loads at a later day. I try to test a load 3-4 times around a week apart to get a true idea of actual accuracy. Haveing seen temperatures, and conditions affect a loads performence Its better to be sure. I also tend to test at full distances when posible. I have seen loads perform good at 200 yds and fall apart at 600 on out. One group is a possible fluke, a days good groups over the day is that day, a loads good grouping over 304 days a week apart each is accuracy

[Bent Ramrod]

I usually use 5 shot groups for load development. However, they are gauged in the context of the other 5-shot groups I fire while varying the charge weights of that particular powder. Generally (especially with smokeless loads for cast boolits) I can see a pattern as the powder charges are increased. The groups get smaller up to a point, and then come apart, sometimes pretty spectacularly. With jacketed bullets this is not as immediately apparent, so generally I just pick a a powder charge from a good group in the middle of the tightest ones and load up more of that for next time. If the groups maintain themselves, that is "the load" for those particular components.

I don't see how a single three- or five-shot group from one load picked at random from a Handbook or recommended by a friend would tell the shooter anything about the accuracy potential. A ten-shot group might, if all shots were very close.

[Bigslug]

Just want to pose a couple of simple questions to satisfy my curiosity.

When you shoot a group to determine the firearm's group size, how many shots do you use? 3? 5? 10?

Depends. I'll do five on a hunting rifle. Not because I expect to fire five, but because I want to know if it has any quirks with regards to warming up and what they are. A competition gun needs the ability to slam X's throughout the entire string, whatever that might be.

How many errant shots do you discount as ' fliers ' ?

Part of being a good shooter is being able to spot your "pilot errors" as you make them. If the fault was mine, I'll note it and throw another round on the target. True "fliers" are the ones you can't account for, and I don't discount those - but rather look for the frequency of their occurrence.

And how many groups do you measure and average to determine the firearm's average group size?

Fired over how many days?

My handloading process has evolved at least as much to minimize the effects of inevitable variations in brass, powder charge, temperature, etc... as it has to reduce them. Once I find "The Load" I'm usually pretty confident that it's not going to do anything different on the next trip to the range. To my recollection, this has only failed to work out once, and this was on a double .45-70 with so much extra variability built in that ammo was but one of the many head-scratchers involved.

[44man]

Mine are an average over time with 5 shot groups. If you "CALL" a flier, ignore it. But those that were not your fault will be due to the brass case most of the time, remove that case from testing.
10 shot groups or more are fine but you just use more brass that might not be right.
BR shooters sort brass and use the same 5 over and over for record. They load the same cases at the bench, over and over for each relay. A pound or so different in case tension will be a flier.
Even the dies you use will make or break groups. Too many just make a "bang".

[SteveS]

I shoot a couple of revolvers so six and twelve shot groups is what I go by. Ten groups tells me pretty much all I want to know.

[Hannibal]

The responses received thus far essentially confirm what I already suspected. Other sites I have visited are full of reports of sub-MOA groups from pretty much every make and model of firearm made. Those same reports are few and far between here. I myself have not found that to be the case. I began to wonder if I just had the worst luck ever when purchasing a firearm? But upon closer reading i was able to deduce a common theme. It is apparent that few or perhaps none here are picking the best group ever fired and declaring that to be the firearm's group size, either. The other sites? Well, not so much.
Thanks to all.

[Outpost75]

http://ballistipedia.com/images/3/33...rubbs_1964.pdf

[TXGunNut]

For group testing I'll fire five shots and if a load shows promise I'll load ten more and fire two more five shot groups. I generally re-test another ten rounds on another day before I settle on a hunting load. I ignore called fliers but look for a pattern on others. Sometimes it's an undetected boolit or case defect but sometimes it's something else. I don't shoot large numbers of MOA groups but that's probably because I'm not an MOA shooter.

[Larry Gibson]

Expanman

When you shoot a group to determine the firearm's group size, how many shots do you use? 3? 5? 10?

A 3 shot group, especially if small, tells you nothing about accuracy potential of the load. If large the 3 shot group tells you things aren't going to get better. A 5 shot group can give you an idea of potential but still can many times be misleading. The reason is statistical random dispersion of shots in the group (cone of fire actually). Statistically it takes a minimal 7 - 8 shots for some surety. A 10 shot test string is the SAAMI standard for testing accuracy, velocity and pressure. Thus I use most often, unless just testing for potential velocity and pressure range, a 10 shot test string with both rifles and handguns of any action type. With 6 shot+ revolvers I many times use "twice around the cylinder" using all the different chambers for 12+ shot test strings.

How many errant shots do you discount as ' fliers ' ?

I do not "discount" flyers. I will discount 2 "called shots" out of the group though which still leaves 8 good shots for surety. Do you know the difference between a "flyer" and a "called shot" out of the group?

And how many groups do you measure and average to determine the firearm's average group size?

I use 3 ten shot groups to confirm accuracy potential of the load in a particular firearm. They may be fired the same day or days apart. "Average group size" is a meaningless term even though we all use it. It means 50% of the groups will be larger and 50% will be smaller. Seldom will any group be the "average". I prefer to use and "ES" (extreme spread) of say "1 to 1.5 moa capable accuracy".

Fired over how many days?

As mentioned for accuracy testing shooting the groups on the same day or other days, if you are a consistent shooter yourself, doesn't matter. However, if determining the "zero" accuracy capability of the rifle I prefer to shoot 1 shot on various days at different times of the day under different conditions. Usually at the "zero" range of the firearm. All shots are on the same target so at the end of 10 shots on 10 different days under different conditions I know how accurate I am with that load and rifle for hunting.

Larry Gibson

[shooter93]

5 at a minimum but generally 8 to 10 once I think it's the load. As Larry said you have to know how to call shots to start eliminating them. Then I like to know a 10 shot group from cold clean to warmish barrel and sometimes if I expect to shoot the gun a lot I'll shoot till accuracy starts to fade beyond my parameters just to know. I shoot the load I've chosen then in all 4 seasons here and generally speaking that gun never sees a bench again unless I suspect a scope problem if it's scoped. I do the majority of my shooting now a days on my hind feet after I find the load for a gun.

[rhead]

I will have at least one group in varied weather conditions made up with the first shot from a cold barrel then two or three more groups fired the same day from a warmed barrel. When you are hunting the target seldom gives you a chance for a barrel warmer shot.

[edctexas]

There is a difference between most of the gentlemen here and those on some other boards. The vast majority here actually have shot their groups. In some other places, the keyboard did the shooting!

I use tool called On Target. You can record your groups from pictures. Groups can be compared or superimposed over other groups shot at different times or temperatures. This allows you to shoot 3 and take a break and shoot at some other time and compare. It also has neat useful note taking capability.

A "Flyer" is a shot which breaks the neat group. You did everything right but the boolit when somewhere else. A "Called shot" is when you know before or at the bang you did something wrong. Many of us here on this site may lump these shots into our totals. Not all of us are quite good enough to be sure that we goofed up the shot. An example might be: You are at the range squeezing a shot when the chap next to you fires his super whizbanger with a muzzle brake. This might cause you to "call" your shot "off", because you only had one layer of ear protection. The BIG bang caused you to jerk. Plenty of other reasons to blow a shot but that might cause one's shot to go outside of the nice group. The really better shooters can tell that they did something off just as the gun bangs. I'm not quite that good anymore.

Ed C

[reloader28]

I fill the handguns.
Rifles I will run 3-4 until I'm getting I'm satisfied, then I'll run three or four 5-6 shot stings thru them.

If I know I pulled a shot, I discount it.
Playing around with reformed 308 brass and some cast boolits in my 243, I started sorting out the fliers. Then after using only the brass that I'd kept as good, there were no more fliers. All were tight groups.

I've since turned the necks on all these brass and that pretty well fixed the problem.

[44man]

I ran into it all the time at IHMSA when the fellow next to me was shooting 335. Had to wait for him to fire first. Talk about gut rumbling blast!
Brass is your biggest enemy and just shooting a bunch will not prove much except you see groups enlarge and not from the gun's or your fault.