The Ten-Shot Group and I

[BruceB]

When I head to the range for some load-testing, it's extremely rare for me to NOT take ten rounds of each specific recipe to be tested. Occasionally I'll have more than ten rounds per recipe, but almost never will there be fewer than ten.

Why? Lessee here....

1. I get to shoot more! Always a good thing, in my book.

2. More importantly, I get a better idea of the possibilities of the loads in question.

Some years ago, a question was posed to all the manufacturers' ballistics labs and lab personnel by a certain publication (can't recall which one) and they received a surprisingly large number of answers to this question (paraphrased):

"What is the SMALLEST number of rounds per group which you believe yields statistically-valid information about the accuracy of that particular load?"

There was a lot of hemming and hawing and walking-around-the-subject, but when these scientific lads were finally pinned down to an answer, the verdict was surprisingly consistent:

A sizeable majority opined that SEVEN ROUNDS PER GROUP was the smallest number that offered a fair evaluation of the load.

Seven rounds is a lousy number for a properly-anal handloader, such as your humble scribe here. The seven rounds don't fit neatly in boxes, for one thing, where I like to see all those smiling headstamps row-on-row (and no gap-toothed grins). Since the additional cost of three more rounds is meager* at worst, I promptly decided that where possible, the ten-rounder was going to be my baby. I have been using that number for grouping tests with cast rifle loads for a few years, now.

What brings up the subject is that last week I took the M1A out for an airing, with a number of 5744 and 4198 loads with 311466 and a couple others. With one of those 5744 loads, I fired a rather ho-hum 50-yard group of about 2.0" for ten rounds. Nothing radical there, right?

HOWEVER ( I love that word), five of those ten rounds were in a tiny hole which measured just 0.20" center-to-center (measure the ragged hole at its widest and subtracting .30", or one caliber= 0.20")!!! If I had fired ONLY those five rounds to evaluate the load, I would've been tempted to host a parade down the main drag with free beer and hotdogs for all and sundry! As it is, I know that the load may show some promise, but isn't really spectacular, at least at this point. This is of course a much more rational state of affairs, and it's all thanks to shooting ten-round groups.

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* I put an "*" behind "meager" up above, because I was reminded on another Board of just how much I loath and detest the word "cheap", as in, "How can I load the goodest ammo the cheapest (or cheepest) way?"

'Cheap' is a put-down, a criticism, an undesireable state of mind, an INSULT in my opinion. "Low-cost", "inexpensive", "economical", are all virtues and desireable, but DAMN, I hate "cheep" (as too many spell it). End rant.

[leftiye]

Bruce, I've always read, heard,etc that those larger groups almost always have multiple flyers. This is also my experience. Your own example above about the nice group contained in the larger overall group bears this out.

My first indiclination would be to shoot two 5 shot groups. However in cast boolits it may be as well to shoot larger groups, and see what it could do without flyers, also see which loads produce the fewest or most flyers.

[45 2.1]

I've done a lot of testing, just like others, and have found that unless you let the rifle cool well between shots, you will find that the barrel will start walking shots with cast at about 6 to 7 shots. Starting from a cold bore, that load will throw the series of shots in repeatable places and you can call position until the barrel walks. Not all barrels are stable either. If the rifle barrel is walking, just how are you testing the load? I believe that your really finding out what it would take to manage what to do or hold off to get better groups, not testing a load.

[Lloyd Smale]

I test them like i use them. If its a rifle i like to shoot 3 shot groups so barrel heat isnt a factor and i also will do alot of test to find where the first shot will hit out of a cold barrel as i dont do much plinking with rifles other then lever guns. If its a lever gun or a handgun i shoot 10 shot groups. I feel that the way I mostly use these guns a 10 shot group gives me a better idea of how a load shoots. I dont go out and shoot 3 rounds with my handguns and why fool myself into thinking that because it will put 3 or even 6 shots into an inch that it will do it all the time. I shoot them competively at times and when you do you rarely shoot less the 30 rounds before the barrel has a chance to cool. So if a load im shooting is going to open up to 3 inch when it warms up i want to know. Ill average 3 10 shot groups and thats what goes in the record books and I dont discount flyers. You can about bet theres not to many 1 inch groups recorded in my books. VERY FEW handguns will shoot 30 rounds into one inch and id about bet that very few guys are capable of doing it even if the gun is. I for one am the first to admitt that i cant. For my handguns if i find a load that will do 2 inch at 25 for 30 shots thats a keeper load. Very few situations call for more accuracy then that. About the only one i can think of is bullseye shooting. When i take a handgun hunting i take a load thats passed that test and shoot it at 50 yards. There i shoot 3 5 or 6 shot groups and at that range my goal is 4 inch. If a gun will do that it will take game to any range a open sighted sixgun is capable of in my hands.

[Bass Ackward]

In theory, I agree with Bob for rifles and Lloyd for handguns.

But in practice, I usually work and wait the time necessary to maintain composure to allow for fair results before moving on with the testing. The human concentration and fatigue element plays a lot in the wildness of groups of any bullet material and if I want to shoot like a machinegun, that comes with practice AFTER load development. Sometimes loads pass the first test and fail my second which is normal speed, or the third test and then the fourth, temperature.

Range is the third. More important to me is the groups size out to as far as I intend to shoot. Load size in close is good to eliminate human error, but many accurate, sub 2" loads at 25 yards won't hold a 8x11 sheet of paper at 75 for many reasons. And range testing is two phased. One off a rest and then off hand to ensure that " I " am "THE" range limiter and NOT the gun / load.

I have gotten loads that work well when developed and then temperature make them fail the second or third tests. I have some that are sub inch for hunting in cold, but are pie plate killers and lead in the summer. I have one, sub inch load at 2600 fps only above 85 degrees for long range ground hogs. So I need to know their limitations.

So testing for me involves many stages before I .... settle on a load.

[44man]

Since my hangun testing is for hunting, I shoot multiple 5 round groups because that is what the cylinder holds in some of my revolvers and that keeps the loads in the box evenly shot. Besides that, I have only needed one shot on deer even though there are five in the gun.
If I was testing for silhoutte or some other target shooting, then 10 to 20 round groups are called for to heat the gun.
For most high power rifles for hunting, three shot groups are good enough with a cooling off period. Again, for target or other competition, more shots are needed to evaluate not only the load but the rifle itself.
The governing factor is the gun's use. If it is a thin, whippy sporter and is heated to where it starts to walk shots, nothing is learned about the load except it goes bang. For hunting, just take one shot at the same target every 15 minutes and you will learn more about how it performs in the field then blazing 10 rounds out of it.
For the general work most of us do, load testing and just plinking, I see no reason to shoot 10 rounds to add the rifle stress into the pot. I am better served by shooting 5 at a time, let the gun cool and shoot 5 more at the same target if I want a 10 round group. The higher the cartridge's intensity is, such as a Weatherby, multiple three shot groups are better with a longer cooling period.
My question would be, are you testing a load or a rifle and what is the end use?

[1Shirt]

Tend to agree with Bass and range testing at variable distances. Like to shoot 10 shot groups once I have the distance figured out, and am happy if my 10 shot groups jacketed or cast stay inside 2" at 100. Always seems like my flier come on the 7th and 9th shots for some reason, while the 6th,8th, and 10th. come back into the fold so to speak. Like 3 shots at given range to insure the scope and load are on. Like 5 shots for varification of the 3 shots. Like the 10 shot groups for the occaisional one that I luck into that stays around an inch. Also agree with the bbl heat factor, and have done some testing with that as well. One time did a 10 shot group with a shot every 2 min (or as close as I could come to it) with a clean patch down after every shot with cast in a heavy 308. Got about an inch and a half group out of that one. Bottom line, I enjoy shooting, Ienjoy testing, and more will always be better than less!
1Shirt:coffee:

[44man]

Bass has a good point and limiting any rifle to 100 yd's is a handicap and doesn't tell you much about boolit stability past that point.
I have the same problem with guys shooting only 25 yd's with a large bore handgun. I shoot revolvers starting at 50 yd's and go clear to 500 meters with them for fun and to see if the boolit is stable. I have always maintained that the worst load ever will shoot good at 25 yd's but might not keep a single shot on paper at 100 yd's, not very comforting when shooting at deer.
What I have said in my other post is even more important for load testing at extended range with a rifle that is heat sensitive. A good heavy barrel target rifle can take many shots without a problem but a sporter that starts to walk shots when hot will not prove that the load is accurate. You are back to rifle testing and until the walking shots are cured, load testing won't tell you anything unless you slow down the shooting. 10 to 20 or more shots for a group are fun, just space them out unless your rifle can take the heat.
Enter another thing here! If your rifle CAN take heat and maintain tight groups, then there is no better way to test a powder. Now 10 shot groups come into their own. Still boils down to the gun and it's use.

[andrew375]

Statistically 7 shot groups give the optimum results. More shots will give a more precise result but the difference in level of precision is not significant enough to make it worth while.

I always go with shooting the number of rounds per group in testing as you will in the intended application. If it is for a competition that requires five shot groups then that is what you should shoot in testing. Most of my shooting is for score on bullseye targets so I always shoot ten shot groups as a final test. Obviously for hunting my only concern would be where the first shot goes.

[EWOK]

Since I'm just starting with pistols I cann't say as to what I'll do there but with long range rifle that I've shot alot, I used two rounds to test loads to start with. I shoot out my loading room window from a sturdy bench to 100 yards and if two rounds will not touch or be real close why burn three, since this is the measure I used then and it proved to be reliable for me, once a good two shots group was had and if the velocity was good then I'd load three, if that held, then five so I guess it was a ten shoot group after all but not ten round of all test ranges, like I said this always worked for me and I was able to load two, shoot and load two more pretty easy with my setup. If through a complete range of given powder did not produce touching rounds then if I really wanted this powder to work, I'd take the closest group and play with seating depth, if no luck then it was off to a different powder. This may sound long and drawn out but really it was pretty quick and easy and I've got some good loads that way.

[BruceB]

Excellent points from everyone, and I had hoped that the thread would generate some good discussion.

The wide variations of method and technique detailed here are a direct result of one huge factor, namely:

"What do we, as individuals, want our personal guns to do for us?"

Obviously, there's a huge expanse of possible answers to that question.

For MY part, no matter what the rifle may SEEM to be intended to do, my rifles now are primarily bench/target rifles and each presents its own unique challenges and problems. My use of the 10-round load test is one method of imposing some sort of uniformity on the testing process. For the very limited number of jacketed rounds I fire, mainly with an eye to hunting use, I test with five-round groups...these may be as 'much' as 0.5% of a year's shooting, if that much.

This also presents ME, the shooter, with some interesting situations which I have to overcome. A six-pound, squirmy Model 77 in 7.62x39 is a real bugbear on the bench, but when I can make it shoot sub-MOA IN SPITE of the physical challenges, it makes me a pleased and happy feller. Such things as barrel heat, fatigue, poor stock design for what I'm doing with the rifle....all such things only make the process more interesting.

Buckshot has referred on occasion to discarding the widest shots in a group as being non-representative of the actual accuracy of the load, due to shooter failings in shot delivery, unseen wind variations, etc. I also do this occasionally, when it's obvious that the rifle and load are working sufficiently-well to place a MAJORITY of the bullets in a decent group. Consistency in testing with 10-round groups tends to make such results stick out from the rest of the pack, and such results are an easily-noticed indication that there is something useful happening which makes further testing a good idea.

In my shooting log, I post a simple drawing of the shape of each group, with flyers indicated, as well as a measurement of total group size PLUS any noteable clusters....i.e.: 2.1"/10 rds/50 yds, 0.9"/8rds/50yds . I also highlight any outstanding loads with a big arrow in the margin of the log's page. It makes it easy to go back and see what was working on a given day.

I suppose what I'm saying is that I DON'T conform my shooting to my rifles' apparent designed uses, but rather that I make my rifles conform to the way I use them....which is mainly as paper-punchers and cast-bullet test-beds. Although I have the capability and equipment in Der Schuetzenwagen to do load modifications at the range, I find it's better from a time-use standpoint to arrive at the firing point with ten rounds loaded for each variation I intend to test.

This works for my rifles and myself, and I am really enjoying reading about how others in the group approach their test shooting.

[felix]

It all depends on the target and its final disposition. In a BR match, then I guarantee you it ain't the load per se, but the entire system, including the person's ability to perform using that one particular volly of shots. At the river, my personal intent is to make shotgun shells fly as far away from their initial resting place as is possible. I usually limit my range to 120 yards or less to assure close to 100 percent "hits". A "hit" requires knowledge about how soft the material under the shell is, and how close a shot has to be to move the shell a substantial distance. Hitting the shell direct on is a no-no, but must be done every once in while to verify that I estimated the trajectory correctly for the LOAD I am shooting at that moment. So, accuracy depends entirely on the sport. I gave up true BR shooting years ago because of travel time mainly, and that is just an excuse on my part. The real reason is that I am not a WEATHERMAN, and can't judge where Jack Sh...t resides at any one moment. ... felix

[mag_01]

I prefer the three shot group for reasons listed above ---- barrel change---shooter fatigue--eyes---ect.---Anxiety to shoot the perfect group---after all you can repeat the three shot test as many times as you want. All-thou at times I will shoot a five round group.------ Mag

[35remington]

I don't address the number of rounds per group so much as the number of groups for a reasonable evaluation. It just so happens I shoot five rounds per group.

If I shoot one excellent group, it doesn't mean much. If I then shoot a subsequent crappy group what does it mean? Which to believe?

The third group settles all questions for me. Which is why I take to the range 15 of each recipe for evaluation.

More often I load at the range. This hasn't failed me so far, and I am speaking of rifles only. A lot of it is with cartridges that don't heat the barrels much.

As for tube magazine levers, three shot groups with the first two shots most definitive.

[montana_charlie]

I read a long disertation by a guy who says a two shot group is the most revealing.
I didn't understand all of the reasoning, as it dealt with the finer points of 'statistics' and other things I am not learned in.

If anyone is interested in the philosophy, I will try to find the thread.

I seem to remember that he drew fire from just about everybody who responded...but that none of them were able to argue against his theory on a point-by-point basis.
CM

[Larry Gibson]

Rifles; I ususally go with 3 or five shots when working up the load. If the group (100 yards for CF rifles), extreme spread, standard deviation and the mean velocity are what I'm looking for then I will load up 10 rounds of that load for another test. I shoot those 10 shots not faster than 1 shot per minute over the Oehler 35P and for group. That gives me a good idea if it is a good, bad or indifferent load. If the laod is for a match rifle I shoot 22 shots at not less than 200 yards.

Revolvers; 5 shot strings over the Oehler with target at 25 yards. Loads that show promiss based on group, mean velocity, extreme spread and standard deviation are then tested in 12 shot strings (twice around the cylinder as I don't have any 5 shooters) at 50 yards (sometimes at 75 or 100 yards).

Pistols; same as revolvers except finalk test is with magazine capacity at 50 yards.

Larry Gibson

[Mk42gunner]

It depends on the gun for me. I like five shot groups, but I like to shoot more than one group too. I usually take 10 rounds of each load to the range, the only rounds from the group that I disregard are the ones that I have called as fliers, (as long as they are were I called them).

Then too it depends on the day I am having....


Robert