Does this Modern Rimfire Deserve a Second Look?

Most recently, in 2004, Hornady released what was touted at the time as the “heir apparent” to the old double-deuce: the 17 Hornady Mach 2 (HM2).

The 17 Mach 2 uses a .22 LR case (a Stinger case, to be exact) and necks it down to accept a .17-caliber bullet. The result is a faster, flatter shooting small game cartridge capable of picking a squirrel off a tree branch at 100 yards.

It sounded great, but it was doomed for obscurity. Only Hornady and CCI still produce the rounds, and Savage is the only major gun company still chambering the 17 Mach 2. There are several oft-cited reasons for its demise, but I’m wondering if small game hunters should give it a second look.

There is no question that the 17 HM2 offers better small game ballistics than the .22 LR. The Mach 2 boasts a 2,100 feet-per-second muzzle velocity, which generates about 166 ft.-lbs. of energy at the muzzle using a 17-grain bullet. A standard .22 LR, by contrast, only generates about 128 ft.-lbs. of energy at the muzzle using a 40-grain bullet, humming along at 1,200 fps.

Velocity in fps | Energy in ft-lbs

Of course, you don’t kill a squirrel with bullet energy. If you’re a civilized person, you kill it with a headshot, so the Mach 2’s real advantage is in its trajectory.

Zero at 50 yards 0 | Drop and Wind Drift in inches | 10mph Crosswind

Wind drift is similar in this comparison thanks to the .22 LR’s much heavier bullet. But the .17 Mach 2 drops far less than the .22 LR, which allows squirrel hunters to hold nearly dead on at 100 yards, even with a 50-yard zero. That added 50 yards of range can really come in handy in the squirrel woods, especially if you hunt in thick foliage where you might not be able to get much closer before the bushy-tail disappears into the trees.

Those excellent ballistics combine with other features that make the Mach 2 attractive to rimfire aficionados. For one thing, the copper-jacketed bullet leaves less fouling in the barrel and action (at least as compared to a lead .22 LR) and also promotes accuracy at extended ranges. What’s more, unlike other souped-up rimfires, the 17 Mach 2 shares an overall length with the .22 LR. This allows a platform originally designed for the .22 to be converted to the .17.

Of course, the .22 LR isn’t the only rimfire the 17 HM2 must compete with. The most popular .17-caliber cartridge, the 17 HMR, was also released by Hornady just two years before the Mach 2. Many credit that unfortunate timing with the Mach 2’s ultimate failure.

The 17 HMR does pretty much everything the 17 Mach 2 does–only better. Here are the same charts as above with the 17 HMR replacing the .22 LR.

Velocity in fps | Energy in ft-lbs

Zero at 50 yards 0 | Drop and Wind Drift in inches | 10mph crosswind

Thanks to its larger case capacity, the 17 HMR offers better velocity and energy at every distance using the exact same bullet as the Mach 2. It also drops much less (three fewer inches at 150 yards) and is less affected by the wind.

Fans of the 17 Mach 2 might point out that the extra powder in the 17 HMR also results in more muzzle blast, and you don’t need that much velocity and energy to take out a squirrel. If your only shot is at the body, you might be able to salvage more meat if you use the slightly slower Mach 2.

On the other hand, it’s not like the 17 HMR produces tons of recoil. The downsides of a hotter cartridge aren’t really in play with this comparison, so it makes sense that if you’re going to get into the .17 caliber, you’d run with something that offers better velocity and flatter trajectory.

A poor showing against the 17 HMR wasn’t the only reason the Mach 2 had trouble catching on. It also had to compete with high-velocity .22 LR cartridges like CCI Stingers. The 17 Mach 2 still drops less than half as much as the 32-grain Stinger at every distance out to 150 yards, but those high-speed .22 LRs were enough to scratch the itch for hunters who wanted something a little faster.

The 17 Mach 2 also suffered from the fact that it turned out to be more difficult to convert a .22 LR rifle into a Mach 2 than proponents had originally hoped. It’s not enough to swap barrels. To this day, CCI posts a warning on the Mach 2 product page advising against using components that haven’t been specifically designed for the faster cartridge. Hunters who tried to convert their 10/22’s to 17 Mach 2 reported several concerning issues, including split cases, out-of-battery blow-ups, and general unreliability.

To me, this is the most disappointing element of the 17 Mach 2 story. I would love to convert one of my 10/22’s to the 17 Mach 2, and while some report doing it successfully, even those reports come with caveats about various failures to cycle. If an ammo company could come up with a high-speed, bottleneck rimfire that could be used in the 10/22 platform, I think it would be wildly successful–especially given the wealth of aftermarket 10/22 parts on the market today.

Still, even given these drawbacks, I think small game hunters should give the 17 Mach 2 a second look.

At $0.20 per round, it’s about twice as expensive as the .22 LR, but only about 60% the cost of the .17 HMR. As of this writing, Midway USA lists 50-round boxes of 17 Mach 2 for $10, so it’s not cost-prohibitive by any means. For that $10, you’re getting an effective small-game killer that can extend the range of a standard .22 without the overkill associated with the .17 HMR. If you can find a gun chambered in the nearly-obsolete little cartridge, I’d say it’s worth a shot.