When it comes to evaluating the accuracy of your rifle, how many groups of how many shots each should you fire? This has been a long-standing argument among rifle shooters and you’ll find that different gun magazines offer different evaluation standards depending on the gun, chambering and range.
For example, I review a number of rifles each year for the National Rifle Association’s American Rifleman magazine. Their testing criteria for center fire rifles requires that I shoot five, five shot groups from a solid rest at 100 yards. Generally, they report the best group, the worst group and the average.
With rimfire rifles the test protocol is different. They require five, 10 shot groups to be fired at 50 yards from a solid rest. The same results – the best, worst and average are reported.
Harris publications testing protocol for rifles require that each rifle be tested at 100 yards and that three, five shot groups be fired. Generally, regardless of the publication, a sampling of at least three loads from three different manufactures is required.
From a reader’s standpoint, I’m not sure how relevant any of this really is unless all the results are really good or really bad or just average. I’ve been shooting long enough to know that just because one rifle will shoot itty-bitty or really bad groups with one load means very little. Rifles and ammo are like people; some combinations just do not mix well. On the other hand, if a rifle shoots all three loads very well or very bad, you could consider that a reasonable indication of how that rifle shoots.
For those of us who want to conduct an accuracy test to determine how well a particular load – factory or handload – will shoot out of our rifle, our testing is specific for a single combination. You may want to determine if a certain load is accurate enough for hunting, for match shoot or for personal defense. You will probably have your own minimum performance standard and what that is or should be is another subject entirely.
The question before us is how many groups of how many shots do you need to fire to answer your question? I wondered the same thing, just because a certain magazine demands a certain protocol, or because a certain test method has become accepted does not necessarily mean it is the only way to answer a question.
And, to further complicate the process, if you engage in shooting competitions where you must shoot the best 10-shot group possible, then that is the way you should test your ammo. The same type testing procedure could also be advisable if you’re testing ammo for a high volume varmint shooting. On the other hand, if you are testing ammo for your deer rifle, its ability to shoot 10 consecutive shots into the same hole is, well, immaterial. In most cases a deer rifle needs to fire no more than three accurate shots in a row.
Point being; conduct your testing based on the application. If you are not writing a review for a magazine that demands a certain test protocol, then who cares what they think.
To get an idea of how different the results would be if different testing protocols were used, I conducted an experiment with two good shooting .22 rifles at 50 yards. The following groups were fired with each rifle:
1 – 10 shot group
5 – five shot groups
5 – three shot groups
5 – two shot groups
5 – two shots groups
This totals 22 groups and 110 shots. Averages were established for the multiple group tests as well as an overall average for all 22 groups. And, the two, five, two shots group tests were combined to provide data for a 10, two-shot group test. What did I learn?
By comparing each test protocol to the over all average it was found that with both rifles the five, three-shot group test was the closest to the overall average. Maybe the most interesting discovery was that I generally fired at least one bad group out of five or at a minimum, one bad shot out of 20.
Shooter skill is an important element of the equation because none of us are Walt Berger perfect. Even if you have a perfect bench set up you are going to make a bad shot. And, that bad shot will ruin the group it was in. The problem is, it can be impossible to sometimes identify if a particular bad shot was actually caused by you. For this reason, firing a single group of any number of shots is not a reliable evaluation. Consider this too; the bad shot you make, might actually correct a shot that would have went wide due to the ammo / rifle combination.
The hard to quantify human element is why the more groups you shoot, regardless of the number of shots per group, is more important. However, once you start firing more than five shots per group, the chances for each group to include a bad shot due to your shooting increases exponentially.
As a friend used to say, anyone can shoot nine good shots in a row, its that tenth one that’s a bitch. Think about it, how many great five shot groups have you ruined with the last shot?
When it comes to conducting an evaluation of my personal rifles I use three-shot groups most of the time. But, I do not get all bent out of shape about the exact size of each group. Instead, I establish a benchmark of performance that I expect or feel I need for each application. I then start shooting three shot groups. If the rifle and I can keep 80% of the three shot groups fired (four out of five) within the standard I have set, I quit worrying about accuracy or the exact size of each group and move on. This means that I can, with confidence determine the accuracy potential of a particular load by shooting less than a box of ammo. If my standard is 1.5 inches at 100 yards and the first two groups measure more than that, I’m done. No reason to test that ammo any longer.
This is exactly what I did with a Ruger Model 77 International in .250 Savage that I picked up for a steal. The rifle had some problems with bedding and the trigger was terrible. I could not get three shots to cluster inside two inches. My intention was to use the rifle for whitetails here in the West Virginia hills and as long as it would consistently shoot three shots into sub 1.5 MOA groups, that was all I needed.
After working on the rifle’s stock and bedding, and after installing a Timney trigger, I started handloading for it. The first load I tried, 35 grains of H4895 behind a 100 grain Nosler Ballistic Tip, which left the barrel at just a shade over 2800 fps, printed four, thee-shot groups in a row at 100 yards and they all measured less than 1.5 inches. In 12 shots I was done, no use to fire another group, which would have likely included the bad shot I was destined to make.
The other day I decided it was time to double check this rifle’s zero before hunting season so I stepped out to the bench and fired one, five-shot group at 100 yards. I took my time to make sure every shot was broken as clean as possible. The resulting five-shot group measured 1.38 inches.
Proof of concept!
For hunting rifles, as long as four out of five of your three-shot, bench rest groups are within your performance mandate, you’re good to go. But you know what? For hunting rifles, your bench rest groups mean nothing unless you have a good bench you carry along in the woods with you. Nope, for hunting rifles its more important that you evaluate your and your rifle’s ability from field shooting positions.
How do you do that? Well, that’s another thing altogether.