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.

The accuracy, flat trajectory and downrange punch of the .17 Mach 2 makes it effective with body shots on gray squirrels out to 125 yards.

.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.

Rimfire hunting options, left to right: .17 Mach 2, .22 LR, .17 HMR, .22 WMR, .22 WRF.

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.