Some 2.5 billion rounds of rimfire ammunition are produced in the United States each year. There are a number of reasons for this--low cost and a high fun factor are two of the most influential. In the right situations, rimfire cartridges and guns make great hunting tools. With that said, let's take a look at the available options.

.22 Rimfire

When I was a kid I used the .22 Short for all my small game hunting, but most hunters today opt for the more powerful .22 Long Rifle and its bewildering variety of loadings. Tops in speed are the Stinger and Quik-Shok from CCI, both loaded with a 32-grain bullet at 1,640 fps. No other load comes close to their effectiveness on varmints, but like other hyper-velocity loads, such as Remington's Yellow Jacket and Viper, accuracy can be less than desirable in some rifles. As well, high-velocity loads tend to damage more meat.

High-velocity ammo is commonly loaded to 1,255 fps for a 40-grain roundnose bullet and 1,280 fps for a 38-grain hollowpoint. Some loads are a bit faster than others, but what really matters is accuracy and which style of bullet you choose.

The typical rimfire rifle will shoot some ammunition more accurately than others, so before heading to the squirrel woods, gather up several different loads and a supply of paper targets. Shoot them all and choose the one that delivers the smallest groups.

The rule of thumb for choosing between a roundnose and a hollowpoint is that the former damages less meat, but should be restricted to shots to the shoulder or head, while the latter leaves less for the plate but works when placed into any vital area.

I know a group of squirrel hunters who leave the high-velocity stuff at home and use super-accurate rifles and match-grade ammunition. One hunts with a Remington 40X target rifle, but most use regular hunting rifles built by Anschutz, Cooper and Kimber. The ammunition they use--Eley Tenex, Remington Match EPS (made by Eley) and Lapua Midas M--is not as effective on body shots as high-velocity fodder, but these hunters stick to head shots, so it works just fine for them.

.17 Mach 2

The .17 Mach 2 is the .22 Long Rifle Stinger case necked down for a .172-inch bullet weighing seventeen grains. Maximum overall lengths of the regular and Stinger versions of the .22 Long Rifle cartridge are one inch, but powder capacity of the Stinger is greater due to its slightly longer case. Use of the Stinger case enabled Hornady, who designed the .17 Mach 2, to safely push a lightweight bullet beyond 2,000 fps from a twenty-four-inch barrel, without exceeding the maximum chamber pressure level of the .22 Long Rifle.

Ballistic coefficients for its seventeen-grain bullet and the forty-grain bullet of the .22 Long Rifle are close to the same, but the former shoots flatter because it starts out quite a bit faster. Its high velocity also enables the .17-caliber bullet to deliver the same level of energy downrange even though it weighs less than half as much.

Within its effective range, the .17 Mach 2 offers plenty of punch for hunting small game. Fox squirrels are tough critters, but the first two I shot through the lungs at about sixty yards toppled from the same tree and appeared stone dead before they reached the ground. Meat damage was no worse than with .22 Long Rifle ammo. Over the next few days I made body shots as far away as 130 yards, and while I did not lose a single bushytail, I could tell I was beginning to push my luck at that distance. With solid hits, the .17 Mach 2 kills California ground squirrels dead in their tracks out to 150 yards, but longer shots become iffy as the velocity of that tiny bullet drops off to the point where it begins to lose its ability to expand explosively.

You can duplicate .17 Mach 2 accuracy with .22 Long Rifle match ammunition such as Eley Tenex, but regardless of how that type of ammo is zeroed, it does not shoot flat enough for consistent hits once the range greatly exceeds fifty yards. You can come close to duplicating .17 Mach 2 trajectory with hyper-velocity .22 Long Rifle loads, but the mediocre accuracy of those loads in some rifles can restrict their practical use on small game to about fifty long paces. When it comes to delivering the entire package--accuracy, trajectory, energy and the ability to buck wind--the .17 Mach 2 outguns any .22 Long Rifle load presently available for use on small game.

.17 Hornady Magnum Rimfire (HMR)

The .22 Winchester Magnum Rimfire case necked down, the .17 HMR is loaded by Hornady, Federal, CCI and Remington with a seventeen-grain bullet at 2,550 fps (CCI also offers a twenty-grain Gamepoint load at 2,375 fps). The cartridge delivers almost 25 percent more energy at 100 yards than the .17 Mach 2, but at that distance it falls short of the .22 WMR by about the same amount.

The .17 Mach 2 is a better small game cartridge and the .22 WMR is better for larger targets such as woodchucks and turkey gobblers, but the .17 HMR's flatter trajectory gives it about a twenty-five-yard advantage on small varmints such as flickertails, ground squirrels and prairie dogs.

The biggest competitor to the .17 HMR is the .22 WMR loaded with bullets in the thirty- to thirty-three-grain weight range. For starters, average cost for .22 WMR ammo is about 30 percent less than for the .17 HMR. The .22 WMR is also loaded by CCI with fifty-two grains of No. 12 shot, a pest load option we will never see offered for the .17 HMR. But the .17 HMR shoots flatter. With my rifle zeroed two inches high at 100 yards, I can hold on the head of a ground squirrel standing erect at 200 yards and place the bullet precisely. Considerably more Kentucky elevation is needed when reaching out that far with the .22 WMR. Inside fifty yards there is very little difference in the effectiveness of the two cartridges on varmints up to the size of prairie dogs, but as the range is increased to 100 yards and beyond, the heavier bullet of the .22-caliber cartridge begins to show its superiority.

I won't say the .17 HMR is inherently more accurate than the .22 WMR, but I will say accuracy seems to vary less from brand to brand of ammunition. I rounded up nineteen loadings of the two cartridges and compared their accuracy in a Volquartsen Fusion, a wonderfully accurate rifle with interchangeable barrels in .17 HMR and .22 WMR. Accuracy of the .17 HMR ammo averaged from 0.35- to 0.92-inch for five, five-shot groups at 100 yards with an overall average of 0.71-inch. The .22 WMR ammo ranged from 0.47-inch to 1.26 inches with an overall average of 0.83-inch.

For hunting edible small game and for shooting all varmints ranging in size up to coyotes, I'll take a rifle in .22 WMR without hesitation. But if the rifle is to be used only for shooting varmints smaller than prairie dogs, then I'll live happily ever after with the .17 HMR. Both are great little cartridges.

.22 WMR And .22 WRF

Introduced in 1959, the .22 Winchester Magnum Rimfire (WMR) is a lengthened version of the older .22 WRF. The .22 WRF can be safely fired in rifles chambered for the .22 WMR, but since the latter is loaded to considerably higher chamber pressure, no attempt should be made to fire it in .22 WRF rifles.

In the U.S. the .22 WMR is presently loaded by Winchester, Remington, Federal and CCI, whereas the .22 WRF is loaded only by Winchester and CCI. For many years the .22 WMR was available only with a 40-grain bullet, but it's now offered in 30-, 33-, 34-, 40-, 45- and 50-grain loadings. Muzzle velocities range from 2,200 fps in Federal 30-grain TNTs to 1,555 fps in CCI 50-grain Maxi-Mags.

Bullets lighter than forty grains shoot a bit flatter and expand more explosively than heavier bullets, making them excellent choices for use on small varmints such as ground squirrels and flickertails. The heavier bullets seem to be a bit more effective on groundhogs, but when the target is that big, shots should be restricted to no more than fifty long paces. All .22 WMR loads are a bit destructive when used on small game for the table, and this is where the Winchester and CCI .22 WRF loads come into play. Loaded with forty-five-grain bullets at 1,300 fps, they virtually duplicate the performance of high-speed .22 Long Rifle loads, and in doing so, transform a varmint rifle into a small-game rifle.

The .22 WMR has long been popular among turkey hunters in states where rifles can legally be used to shoot them. Using a rifle to pick off a gobbler at long range is not my cup of tea, but coaxing one inside forty yards and taking it with a single well-placed bullet rather than a handful of shot from a scattergun is far more challenging and a nice change of pace to boot. Best bullet weights here are forty grains and up, and best bullet placement is where the wing joins the body. Even then, it's best to turn down shots beyond fifty yards.