Home Forums Hunting & Shooting Ask The Gunwriters 3 shot groups vs 5? 10?

I've been reading a 1936 book on woodchuck hunting. The author warns against using 5-shot groups for handload development. He says they will give you a misleading idea of the load's accuracy. He recommends averaging two 10-shot groups and comments that a 1.5 inch average is good.

The 3-shot group seems to be the common standard now. There are sometimes comments about how much accuracy is improved with modern barrels and components.

What would some of these modern 0.5 inch 3-shot group rifles do if the shooter averaged two 10-shot groups?

The comment on load testing got me to remembering an old article that had an approximate conversion factor for estimating group size for more or fewer shots. For example, a 3-shot group of 0.75 inches would be multiplied by 2.3 (I made up that number) for the expected size of a 10-shot group.

Anyone remember that article?

Thanks,

Bruce

Bruce: Must be Charles Landis's book.I have a vague memory of the article;there may have been more than one.I happen to agree that 5-10 shot groups do tell you more than 3 shot groups.

That said,I don't believe in shooting 10 shot groups everytime you go to the range.Group shooting is interesting but I prefer to practice MY shooting from field positions instead.

But when I'm learning my way around a rifle,or it's new,or the load is new,I've found that shooting 8-10 shots will disclose accuracy issues more reliably than 3 shot groups;and they will frequently disclose mechanical issues with the rifle itself.

After you do it a couple times,though,you can resort back to the 3 shot routine for zero checks,etc.

Within the last year,I was working with a rifle that held 3 shot groups at about 3.5" at 300 yards;but two shots were always close,and the third was "low",which always opened the group.

I did not think anything of it until I took the rifle to 500 yards and shot a 5 shot group and two shots were about 12" below the other 3(?!)The rifle was double grouping;but it is so accurate that 3 shot groups looked "OK" at 300 and under.I traced the problem to a loose dovetail scope mount.

I have two thoughts on the question: (1) a 3 shot group is too small. You can easily have two shots touch, and a third off, and draw an incorrect conclusion that the load is inaccurate. You can also have a 3 shot group in one hole, and draw the wrong conclusion that the load is more accurate than it is. I think of throwing 500 darts: somewhere along the way 3 consecutive tosses will touch, and another 3 will hit wildly apart. Neither is a true measure of your accuracy. Statistically, three shots is really too small to rely on. I've seen too many shooters chase something that isn't there with small groups. (2) for hunting rifles, 3 shots is really all you need to be concerned about under most circumstances. IF, and only IF the flyers always come from something beyond the third shot, then I wouldn't worry very much. If you put four shots in one hole, and the fifth is wild, for example, that would be OK for me in a hunting rifle.

For hunting rifles, I want to shoot multiple groups at the same target. It really doesn't matter too much to me if the groups are three or five shots, as long as I end up with multiple groups of a minimum of 10 to 15 shots. Really, when you think about it, one of the best measures of a hunting gun's potential might be to shoot ten 1-shot groups, from hunting positions, on entirely different days, at the same target. Where the bullet goes from a cold barrel, the first time, is very important.

I suppose a 3 shot group is very adequate for changing the scope when zeroing a rifle, but it is lacking in giving a clear idea of load consistency.

The bottom line is many 5 or 10 shot groups will have flyers, while some good loads will not. Until you actually shoot the groups you can't have a clue. I would rather have a good load without flyers than an exceptional load with flyers.

If I can get a cold bore shot (fouled OR unfouled; but I don't demand both fouled AND unfouled) to always land at the same exact spot I don't really care what happens after that.

I've seen too many lucky 3 shot groups to have much faith in them. A rifle that will shoot good 5 shot groups is consistent.

I'll bet if you had the author flip through a 2008 Midway catalog he'd re-think his stance on ten shot groups.

Travis

While that article makes a point on a rifle that may be used for multiple shots I find that for some rifles whats most important is where the first shot goes!

That means, in a way, a one shot group!

A rifle that is stable and stays sighted in is most important for many uses.

Not every rifle has such demands. A target rifle might have its impact tested at every match. Thats what we do.

For instance I have a 40X used for free rifle matches. Thats a three position 120 shot match. What matters in that match is every shot. You might say a 120 shot group! Now there is time to clean the bore after each 40 shot string but I have shot the entire match without cleaning.

The details of the demand on the rifle set the testing parameters.

I do both.

I start with 3 shot groups across a broad range. The gun isn't going to shoot any tighter with 5 shots than 3, so I can reject a lot of options with less components with 3 shot groups. Once I've got something that looks promising I go back and reshoot with 5 shots, sometimes more, with more closely spaced increments of powder. If it's something I want to shoot really well, then I'll pick the best load from the 5 (or more) shot groups and vary seating depth to see if that improves accuracy even further.

A friend of mine does something else. He shoots one shot groups. He loads across a broad range of charge weights, 0.2 grain increments, and fires 1 shot per increment tracking where the bullet hits paper. He's looking for areas where the load is stable, where successive shots hit the paper in the same area, staying away from loads that "move" increment to increment. It seems a little funny to me but it works, he's gotten loads to shoot sub inch at 300 yards within 20-25 shots this way, but generally only with trued actions / aftermarket barrels / custom chambers, not quirk-collection factory rifles.

Whatever works for you. Just make sure you compare apples to apples so the results mean something to you.

Tom

I would probably agree that 3 shot groups completely alone do not tell a complete story. But 3 shot groups shot consistently day after day would, for my purposes, tell the complete story of that load and that rifle if it were a hunting rifle. If it was a benchrest or target rifle or even a varmint rifle it would be an entirely different story. I have rarely if ever taken more than 3 shots at any game other than birds during one small period of time. ALL rifles are purpose built and you first have to define the purpose before you can go about measuring the accuracy. That is of course only MY opinion.

That's right. If you're shooting a hard-kicking big game rifle, 5 shot groups are not going to be necessary or desirable. For a varmint rifle, 5 shots is probably a minimum. For a sniper rifle, ?

I've seen way too many rifles shoot a 3/4" three shot group, and then a 4" three shot group.

A load I hunted last year was tested with two shot groups, as it was pretty hot that day. I'd already ran a few over the chronograph on a previous range trip where I was looking for pressure and velocity. When I got to my "range", I set up a paper target at 100yds, another at 250, and a gong at 425. My JBM printout told me that I needed to be 2.5" high at 100 to be zeroed at 250. As the rifle was already pretty close, I shot two touching shots that were right at 2.5" high at 100. After I let it cool down a few minutes, I shot two at 250, with one landing on either side of the 1" bull. After a few more minutes, I clicked out to 425 per my printout and fired two more. They landed right on point of aim, about 2.5" apart. Done deal and I went hunting. I likely wouldn't do that with a varmint gun, but it worked just fine to get me going with this light barreled sporter.

+1, and well stated!

I've been fooled by 3-shot groups, but not by 10-shot groups.

It would make more sense to shoot 10 two-shot groups and then calculate the average.

The problem with the average of two 10-shot groups is that you are really just using four out of 20 shots.

By using multiple groups of fewer shots, you get a better statistical (numerical) picture. On the other hand, viewing a couple of ten shot groups on paper would give a better "real" picture.

I had a very wise statistics prof who told his students to always make a graph along with calculating the numerical statistics. You can think of a group on paper as a kind of graph. Both the numbers and the picture are useful in understanding what is happening.

Paul

I love the statistical mind.

"Well, okay, it's accurate in practice, but is it accurate in theory?"

Read an article some years ago where the author contended that a 7 shot group is the minimum needed to be statistically significant. I forget what confidence level he was going for, IIRC it was 95%.

Am pretty sure the article was in an old "Handloader" - maybe one of you guys that hasn't sold or tossed out your collection could find it?

I think one of the Speer manuals (#13?) may have had a similar statement about a seven shot group.

FWIW, once a few three shot groups have seemed to indicate a possible accurate load, I'll shoot a ten shot group made up of 2 and 3 shot groups all on top of each other. It doesn't make for the pretty bragging groups posted on the internet but it definitely tells you if the combination of you and your rifle is capable of laying'em in the same place shot after shot.

That could very well be it. I'm good at remembering that I remember reading something but not so good at remembering where.

There are a lot more factors then just the technical that play into how many you shoot to 'test'.

To start off there is purpose as others have stated. A big game rifle the 1st cold barrel shot it the one that counts, and sometimes the 2nd, and almost never the 3rd. The Ol' hunter saying, "0ne shot, dead deer; two shots, maybe deer; three shots, no deer." So for a big game rifle I see no problem with three shot groups as long as you can do them from field positions.

Varmint and target rifles have different demands on them and should be developed and treated as such.

Now the real factor is for any group you have to know what you are measuring. Are you measuring the rifle / load combo or the shooters ability. I have shot a fair number of sub one inch groups in my life with five shoots, but never been able to do it with ten shoots. This is not the rifle or loads fault but mine as a shooter. I have my rifles for hunting and fun (plinking) and I am not a target shooter.

To give a real world example I have a Marlin 1895GS 45-70 lever action. Now no lever action is 'easy' to test from the bench. If I start out try to test new 'hunting' loads the first few targets are all over the place regardless. Now if I warm up shooting with some mild plinking loads and get myself settled in with the rifle first, then those hunting loads targets start to mean something.

Remember the shooter is a 'BIG' part of the test here. Now if you have heavy recoiling rifle, how well will you be shooting on shot number 10 to 12 lets say.

The bottom line is that it all depends. Not that what you read was wrong, but rather that it just is not an absolute in all cases.

This is the long way of saying what is important is .... Can you hit what you want when you want with the rifle / load combo ???

If the answer is yes you are fine. If the answer is no then you need to work on it.

Let us stay focused on the purpose and use only the details that get us to where we want to be.