Accuracy can be subjective.
For example, if I said that I had a pretty accurate rifle, but did not clarify that statement, one listener might think that I had a rifle that could shoot .5 MOA (1 MOA = 1.047″ at 100 yards), while another might think that I had a rifle that could shoot 2 MOA. The first guy might think that I based my statement on a single three shot group. The second might think that I fired ten shots.
Which person would be right? Well, they might both be “right.” If I had a rifle that would never put a round outside a 2 MOA circle at 100 yards, I would consider it to be “accurate”. Another person might be totally disgusted with the concept of that rifle and would consider it to be inaccurate and wholly useless for their needs. They might settle for nothing less than .5 MOA.
That’s why we tend to define accuracy in terms of hard numbers, though wiggle room can be found there as well. How many shots make up a group? Does every round count, or can you ignore one or two outlying holes on the target?
Standards for individuals vary. I’ve heard statements such as “Five shots satisfies my definition of accuracy” and “If you’re going to shoot ten rounds, you might as well shoot a hundred”. I’ve also heard statements such as “three shot groups are worthless.” Again, who is right?
I turn to what professional organizations consider to be accuracy testing. When I say professional organizations, I’m talking about the military and large governmental organizations. They’re not messing around, and they have nothing to gain by allowing subpar ammunition and rifles to be purchased. Every one of these organizations bases its accuracy standards on multiple ten shot groups – normally between three and six, but sometimes as many as ten. The average of these groups is used when a weapon or ammunition is being considered for purchase. For example, here’s the most recent (as of this date) FBI 5.56mm ammunition RFP.
But why? Why do they go with ten shots, if three or five shots are “good enough” for a number of people – including, apparently, every firearms magazine writer on earth?
Well, groups don’t tend to get a whole lot bigger after ten shots. A three shot group might quadruple in size by the time it becomes a ten round group, but (barring some outside influence or weapon/ammunition failure) it would be exceptionally rare for a ten shot group to quadruple in size by the time it becomes a twenty or thirty shot group.
“So what,” you say. “If I can put three rounds in an inch at 100 yards, that makes me a marksman of the highest order, and my rifle second to none.”
Well, there’s a big problem with that, but I need to define a few terms before I go on. Point of aim (POA) and point of impact (POI) refer to where the shooter intends to place a round, and where the round hits the target, respectively.
At the Range with a Rifle that can shoot 1 MOA “All Day Long”
Let’s assume the following about a shooter and his rifle.
– The weapon is properly zeroed for the ammunition to be fired
– The target is at a known distance and the weapon is zeroed so that point of impact is the same as point of aim
– There are no outside influences such as wind to interfere with the flight of the bullet
– The shooter is well rested and the weapon is supported in the same manner as when the weapon was zeroed
Now, if that shooter claimed to have previously fired a 1 MOA group, I would assume that his claim meant that the next round out of the barrel would land within 1/2″ of his point of aim – in this case, the bullseye. And if he had just fired a 10 shot, 1 MOA group, that would most likely be right – if the round was more than 1/2″ away, it wouldn’t be very far. However, if he had just fired a 3 shot group, he might be surprised to find that that round was way more than 1/2″ away.
He could fire a few more rounds, and they might or might not be close to the bullseye. They might or might not be “sub-MOA” in relation to one another. But when one collects a number of 3 or 5 shot groups that have been fired consecutively (with no change in any factor that relates to accuracy) and overlays them, invariably, they become larger. How much larger? That depends.
There’s no real way to translate the accuracy shown by a 3 shot group to that shown by multiple 10 shot groups. There is no honest way to compare a rifle that shoots 1.5″ 10 shot groups to one that shoots .75″ 5 shot groups. Why do people insist on using three and five shot groups as standards for accuracy? Because they become frustrated with the performance of their weapon in relation to what they see or hear on the internet or in magazines, especially when they shoot ten shots. They back their groups down to three and five, throw out “fliers” and “bad groups”, and report great accuracy just so they can fit in.
What is Accuracy?
You see, an accuracy claim isn’t simply representative of past performance – it’s essentially a guarantee of future performance. One three or five shot group only tells you what your rifle did one time – a number of ten shot groups, averaged out, tells you what your rifle can do every time.
Accuracy is ATK saying to the USMC: “This ammunition will not shoot groups any larger than 2 MOA out of an M4 Carbine”. It is a rifle manufacturer saying to you, a customer: “This rifle will not shoot groups any larger than 2″ at 100 yards.” It is you saying to yourself: “I know that the next round I fire from this weapon will be within 1 MOA of where I intended it to go – no exceptions.”
So the next time you’re at the bench shooting for small groups, don’t throw anything out. Don’t ignore a few supposedly errant shots so that you can feel better about yourself or your rifle. Don’t be ashamed if you can’t match what you see in a magazine or online. Look at the big picture – overall, what was the rifle capable of? I find it ironic that some of the most inaccurate claims regarding a rifle’s performance are those relating to the mechanical accuracy of the weapon.
Much credit has to go to Molon for his tireless work towards educating the “internet public” about this topic, especially his thread on AR15.com titled “The Trouble with 3-Shot Groups“.