On rimfire ammunition and accuracy

Monday, June 16, 2008 Filed in: Ammunition, General gun stuff

Serendipity, that's what it is. Last week a consistent topic kept coming up in a variety of places: the necessity (or lack thereof) for "accurate" .22 long rifle ammunition.

 "I don't shoot groups, I hunt {insert favorite furry tidbit here}."
"You can't shoot really accurately in the field anyway, so better ammo isn't worth the price."
"The ammo already shoots better than I can, so I just buy whatever is cheapest."

I believe such comments to be shortsighted. First, though, a bit of information for those not intimately familiar with the vast array of rimfire ammunition.

The .22lr is the most popular (by a huge margin) cartridge in the world. It is available in a bewildering number of forms, from the very cheapest to the "ohmigod, I could buy a good steak dinner for that amount of money!" In general, the more accurate the ammo, the more it will cost.

The odd thing, however, is that not every .22 gun (be it rifle or pistol) will necessarily shoot the most expensive ammo into the smallest group. Rimfires are notoriously finicky; you can, quite literally, take two different .22 rifles, of the same model and vintage (and very close to the same serial number) and each will have very different ammunition preferences. Sometimes the most expensive will in fact shoot the best; other times, a less expensive fodder will do the deed.

In terms of consistency, however, the more costly ammunition will win out - it simply won't vary as much from group to group, even if its absolute accuracy isn't as good. In other words, a cheaper ammo may produce a smaller group occasionally, but the more expensive stuff will shoot the same size group all the time. In the aggregate, the more expensive the ammunition, the more likely it will shoot better in any given gun.

There's no guarantee that you'll set records with more costly bullets, but it's a dead certainty that you won't with WallyWorld specials!

Back to the subject at hand...let's say that you have a rifle that at its absolute best is capable of shooting the magic 1 minute-of-angle (MOA) group (which is, for all intents and purposes, 1/2" at 50 yards.) What this means is that the group it shoots with its best ammunition choice will fit into a circle measuring 1/2" in diameter. Clear so far?

Assuming that the actual center of the group is at the actual point of aim, any shot fired will fall a maximum of 1/4" from the point of aim; this is known as 1/4" radial dispersion. If one shot lands at the extreme edge of that dispersion, and the next at the opposite side of that dispersion, the distance between them will be 1/2", which is the group size. See how that works?

Now, let's say that some other ammunition shoots 4 MOA in this rifle (2" at 50 yards.) Any shot that is fired will now land within 1" of the point of aim. That's still not bad; certainly not enough to even get you in the door at an Olympic training village, but enough to nail pop cans off the fence.

Or is it?

A standard 12oz pop can has a diameter of 2.6", or 1.3" on either side of the center. Aiming dead on that center point, with our 4 MOA ammo, means that the worst shot of the bunch only has .3" to spare to knock the can off the fence. In other words, with that ammo your aim and hold has to vary no more than .3" if you expect to hit the can with any given shot!

Will the better ammo give us an edge? You tell me...with 1 MOA ammunition, the expected radial dispersion is .25". That means that any given shot, holding absolutely dead center, now has a margin of error of 1.05". In other words, your aim and hold now has a bit over an inch of leeway to hit with 100% certainty. I'd say that's a significant advantage, wouldn't you?

Shooting is all about being able to trust your skills, but you can't get to trust your skills until you first can trust your equipment. If you practice by popping cans off the fence, how will you know if that miss was because of your skills, or because of your equipment - and is it the ammo, or the gun?

Someone will no doubt be yelling at his (or her) monitor that not every shot will be at the outer edges of the variables. In other words, an ammo that shoots 4 MOA will distribute shots all over that circle; not all of them will be in the center (otherwise it would shoot better than 4 MOA), but likewise not all of them will fall on the edge of that circle. This is true.

The trouble with this line of thinking is that we don't know where any given upcoming shot will fall. We know that it may hit in the center of its expected circle, or it may hit at the edge, or somewhere in between. We don't know where it will hit until it does; if we expect to hit the target with every shot, we have to assume the worst and prepare for it, looking on anything else as a wonderful happenstance.

It's all about probabilities. Let's take our 4 MOA ammo; it's possible that, say, 80% of its shots might fall within a 2 MOA circle. This means that 80% of the time, you have a bit over 1/2" of leeway on that pop can. Put differently, if you can aim and hold within 1/2" of center, you'll hit the can 80% of the time. If you're happy with 80%, great! (Yes, I'm aware that you can increase the hit probability by simply decreasing the distance to the target. If you're going to shoot everything from 20 feet away, you may feel free to use the worst ammo in the worst gun, and never have the need to improve your skills. Everyone wins - sort of.)

Personally, I'm not enamored with those numbers. Look at it from my perspective: I like to hunt small game with my .22 rifles, both for pest control and dinner. I'm an old farm boy who has a close relationship to the animals around him; if an animal is to die by my hand, I require that death to be as humane - quick and painless - as is possible. For me, that means headshots and instant incapacitation. If you eat small game, you know that head shots are necessary simply to maximize the amount of usable meat from the ammo. Squirrels aren't all that big to begin with!

Further, a missed shot is a lost animal; unlike targets and pop cans, they usually don't wait around for you to try again. I want 100% hit probability if I can supply the necessary foundation (sighting and hold.)

A small animal's head often has a kill zone of around 1-1/2" (even less if forced to take a frontal shot.) If I were to use ammunition that only shoots 4 MOA, that would require me to have absolutely zero error in both sighting and hold to make a clean kill at 50 yards. (Actually, it has negative error - meaning that even with perfect performance on my part, I cannot expect the ammo to deliver a clean hit 100% of the time.) At 25 yards, it doesn't get a lot better - my total allowable aim/hold error for a clean kill is a whopping quarter-inch! Can you do that from a field shooting position? Really? Every time?

Switching to the better ammunition gives me a big edge. At 50 yards my self-induced error allowance is now a half inch, and at 25 yards it is almost 3/4". It means that the chances of a successful clean kill are significantly improved by using the better fodder.

Higher quality .22lr ammunition isn't just for benchresters and group junkies. If one is just starting out, it means faster and surer skill development. For the hunter, it means greater yield and more humane treatment of the animal. In my mind, it's worth the price.

The only thing left is to get a whole bunch of different kinds of ammunition and test them all in your gun. You'll learn just how much you'll have to pay to get the accuracy you really need - not the accuracy someone insists you can settle for!

 -=[ Grant ]=-

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