October 23, 2013
How Many Shots Does It Take to Measure a Rifle's Accuracy?
By David E. Petzal
The question has been asked, is a three-shot group as worthless as Congress, and is the five-shot group the only true measure of a rifle’s accuracy?
This is a complex question, and requires a two-part answer. Part one: Nothing is as worthless as Congress. Nothing. Part two: It depends.
Back in the days of Harry Pope (which is to say the late 19th century and the early 20th) the ten-shot group was standard. If you used anything but ten rounds to verify a rifle’s accuracy, you had something to hide. But then, I would guess around 1950, five shots became the standard, and after that—I’m damned if I can put a date on it—three.
There were sound reasons for this. As far as a big-game rifle is concerned, any number of shots beyond three is academic, because not once in a blue moon are you going to get to fling five rounds at a big-game animal. I can remember doing this only five times; there may have been other occasions, but they’re very few.
There are other reasons. First, if your rifle will put three in a tight little cluster, it will almost certainly put five in a slightly larger one, and what difference does it make? Second, if you do a lot of shooting, relying on 5-shot groups can get very expensive very quickly. Also, if you shoot big guns, relying on five instead of three is more painful. If you’d like to make sure your .458 Lott will give you match-grade groups why, have at it. Never mind that it will be used on something that weighs over 1,000 pounds and is only 50 yards away—enjoy yourself.
Manufacturers who fire test targets to send along with their guns use three shots because when you’re doing that with thousands of rifles a year, it really gets expensive, and going to five is just not economically feasible.
On the other hand, a five-shot group is a much truer test of a rifle’s accuracy. The statistical experts among you may want to correct me on this, but it’s probably twice as hard, or a bit less, to shoot a good five-shot group as it is a three, because each time you pull the trigger there is so much that can go wrong.
For some rifles, three-shot groups are of little use. This includes anything that is going to fire more than three rounds in the course of business, and includes prairie dog guns, tactical, benchrest, and any rifle that will be used in NRA-sanctioned competition, where you fire multiple 20-rounds strings.
But for big-game rifles, three is it for the foreseeable future. Doubtless we’ll someday have rifles and ammunition that are so accurate all you’ll need to do is fire one shot to get your zero and that will be that. I can wait; it will be a much duller world.