Big guns are sexy, but little guns are useful. For those who spend a great deal of time in the outdoors, particularly in rural areas, rimfires are often the daily workhorse. Whether it’s taking care of problem animals, keeping your skills sharp, or teaching new shooters the ropes, rimfire rifles are very useful tools that often see everyday use. In my area, I’ve noticed a shift among farmers and ranchers away from larger cartridges and toward the tiniest of bores, the .17. For decades, factory .17-caliber cartridges have been available, but only recently have they been for rimfires. The newest on the block is the 17 Mach 2, and it’s a serious contender as an all-around small game round.

17 MACH 2

The 17 Mach 2 cartridge was released in 2004 and is essentially a CCI Stinger 22 LR case necked-down to 0.172. Stinger cases are 0.100-inch longer than the standard Long Rifle and were determined to be a better fit for the cartridge. In short, the 17 Mach 2 is to the 22 LR as the 17 HMR is to the 22 HMR — same basic case, smaller diameter bullet. The result of the smaller and lighter projectile was a predictable and impressive gain in velocity, double that of the 22 LR in many cases. A 17-grain bullet moving at over 2,000 feet per second has a permanent effect on small game and, most importantly, almost never exits due to its violent expansion. If you’ve ever faced the challenge of safely dispatching a pest animal in a suburban neighborhood, you can appreciate the virtues of such a cartridge.

The 17 Mach 2 fits in sort of a sweet spot among rimfire cartridges: It’s faster and flatter than the 22 LR, yet has less muzzle blast and sound signature than the magnums. That said, ammunition options are limited, with Hornady and CCI each producing a pair of loads. Hornady produces a 17-grain Varmint Express load that uses the V-MAX bullet and a 15.5-grain NTX lead-free offering. CCI also loads a 17-grain V-MAX along with product that uses a 17-grain VNT load. Each of these loads has an advertised velocity of 2,010 to 2,100 fps, with the Hornady ammo clocking the upper end of the range. With a 100-yard zero, the 17-grain Hornady pill drops 14 inches at 200 yards, roughly half as much as the average 22 LR at the same distance.

Disassembly requires only a small punch — a pen will do in a pinch. With the bolt removed, the A17 can be cleaned from the breech.

The 17 Mach 2 has struggled a bit in popularity for a variety of reasons, timing being one of them. Not only was its release overshadowed by the faster 17 HMR, its launch during the Obama-era ammunition shortages ensured that few shooters could get their hands on any. At this time, Savage Arms has been the only major rifle manufacturer to embrace the round, though Volquartsen does offer its Summit rifle in 17 Mach 2. Savage offers both bolt-action and semi-automatic examples, including the A17 HM2, which we obtained for testing.

SHOOT, RINSE, REPEAT

The A-series of rifles includes models chambered for the 22 LR, 22 WMR, 17 Mach 2, and 17 HMR. Building a rimfire semi-auto isn’t necessarily as easy as it sounds, and each of the cartridges has its own individual challenges. The 17 Mach 2 operates at significantly higher pressures than the 22 LR, and a blowback design engineered for the latter is likely to be a failure when chambered for the faster round. Thin brass combined with high pressures can lead to case splitting, particularly when the case head isn’t supported. If you’ve ever wondered why some 17 HMR semi-autos have failed, this is the reason — one can’t simply scale-up a blowback design and expect it to work safely and reliably at such pressures. Simply beefing-up the bolt can help, but it can also present its own problems.

Light, accurate, and relatively flat-shooting, the A17 is a great all-around woods rifle, so long as big game isn’t on the menu.

Hornady’s own research encouraged Savage’s engineers to solve the pressure problem. “The cartridge was a little too much for most standard rimfire actions, and so, shortly after launch, the gun manufacturers pulled the semi-autos,” Jason Hornady, the company’s vice president, told us. “A rimfire is way more fun in a semi-auto than a bolt gun. Well, we’re friends with the Savage folks, and they introduced the A17 in .17 HMR — we shared our Mach 2 numbers with them and suggested they do a rifle in that cartridge. In under a year, they had a gun that’s kickass. They sent us a couple to test: We threaded one and put a suppressor on, and it might now be the baddest rimfire varmint rifle out there.”

So how did Savage fix the problem? They developed a unique delayed blowback system for the A17. Delayed blowback prevents premature rearward movement of the case that would allow for case head failure at the peak pressure spike. Basically, the case stays in the chamber longer, which both supports the case head and allows the pressure to abate.

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