.17 HM2
From Wikipedia, the free encyclopedia
| .17 Hornady Mach 2 | ||
|---|---|---|
| Type | Rimfire | |
| Place of origin | United States | |
| Production history | ||
| Designer | Hornady | |
| Produced | 2004 | |
| Specifications | ||
| Parent case | .22 Long Rifle Stinger | |
| Bullet diameter | .172 in (4.37 mm) | |
| Neck diameter | .180 in (4.57 mm) | |
| Shoulder diameter | .226 in (5.74 mm) | |
| Base diameter | .226 in (5.74 mm) | |
| Rim diameter | .275 in (6.99 mm) | |
| Case length | .714 in (18.14 mm) | |
| Overall length | 1.00 in (25.4 mm) | |
| Primer type | Rimfire | |
| Ballistic performance | ||
| Bullet weight/type | Velocity | Energy |
| 17 gr V-Max | 2100 ft/s (~640 m/s) |
166 ft·lbf (~226 J) |
| Source: Hornady | ||
The .17 Hornady Mach 2, or .17 HM2, is a rimfire cartridge introduced in 2004 by the ammunition manufacturer Hornady, following the successful launch in 2002 of the .17 HMR. The .17 HM2 is based on the .22 Long Rifle case, slightly lengthened and necked down to .17 caliber (4.5 mm) and using a bullet weighing less than half what typical .22 Long Rifle bullets weigh. That ultralight bullet is a key part of achieving the very-high velocity for a rimfire round, but it produces compromised performance on the other end when it hits.
The .17 HM2 may or may not live up to its name, depending on your geographic location and conditions, with velocities out of a rifle of 2100 feet per second (640 m/s). The velocity is double that of a standard .22 Long Rifle, and that velocity generates a much flatter trajectory out to the 150 yard (140 meter) effective range of the cartridge. The tiny .17 caliber jacketed bullet is much more difficult to manufacture than the copper plated lead .22 Long Rifle bullets, and that is reflected in the cost--5 times that of inexpensive .22 Long Rifle ammunition. The price is still less than any but surplus centerfire ammunition, and less than the more powerful .17 HMR. The high priced bullet used in the .17 MH2 does have its advantages, and accuracy is one of them.
Since the .17 HM2 is based on the .22 Long Rifle Stinger, converting most firearms to .17 HM2 requires only a barrel change. The higher pressures makes conversion of semiautomatic firearms more difficult, as virtually all are blowback designs that are sensitive to pressure changes. Kits for the Ruger 10/22 have appeared, and they replace the stock aluminum bolt handle with a heavy, weighted handle to increase the bolt mass. Since the .22 Long Rifle is arguably the most popular cartridge in the world, the .17 HM2 has a large pool of potential firearms that could chamber it, and a huge infrastructure to manufacture the rimfire case it is based on. The .17 HMR was an instant success when it came out, but the .17 HM2 hasn't been out long enough for its success to be judged. Part of the .17 HMR's success may have been due simply to the uniqueness of the first mass manufactured .17 caliber rimfire (.17 Aguila was first, but never mass manufactured), an advantage the .17 HM2 doesn't have. However, the .22 Long Rifle outsells the .22 WMR by a huge margin, and if the .17 HM2 can build on that success, it has the potential to go far.
