.17 Hornady Magnum Rimfire, commonly known as the .17 HMR, is a rimfire rifle cartridge
developed by the ammunition company Hornady in 2002. It descended from the .22 Magnum
by necking down the .22 Magnum case to take a .17 caliber bullet. Commonly loaded with
a 17 grain bullet, it can deliver muzzle velocities in excess of 775 m/s.
Development
The .17 HMR round is similar to rounds developed by dedicated rimfire wildcatters who worked
to create a rimfire cartridge with an exceptionally flat trajectory. These wildcatters were seeking
to match the ballistics of the obsolete 5mm Remington Magnum Rimfire, which was made from
1970 to 1974, and was to that point the fastest rimfire cartridge ever produced. With 5mm
diameter barrels and bullets being virtually unavailable at the time, the commercially
available .17 caliber became their bullet of choice. The .22 Winchester Magnum Rimfire
was the logical parent case, rather than 5mm RMR, because it was commonly available, and
it is a far larger and stronger case than the next largest .22 Long Rifle. The .17 caliber
wildcats not only met, but far exceeded the 5 mm RMR's velocities and flat trajectory.
The accuracy of these cartridges was also quite good. However, the downrange energy
of the 5mm RMR is superior to both .22 WMR and .17 HMR, so there is still potential in
the 5mm rimfire for wildcatters. Hornady, in conjunction with Marlin Firearms
and Sturm, Ruger, followed much the same path. With the .22 WMR case as the starting point,
a simple barrel change was sufficient for most .22 WMR firearms to chamber the new cartridge.
In 2002 the first rifles and ammunition began appearing on the market. While the ammunition
was relatively expensive due to the high-performance .17 caliber bullets used, it was still cheaper
than most centerfire ammunition. By 2004 CCI, Federal Cartridge and Remington had each introduced
.17 HMR ammunition offerings. Availability
Cartridges for .17 HMR come with bullets that weigh 15.5-grain, 17-grain, and 20-grain,
and come in designs such as polymer tipped, hollow points, soft points, and FMJ. The terminal
ballistics of the lightweight expanding bullets limit the .17 HMR to small game animals and
varmints. .17 HMR ammunition is less common and more expensive than the .22 caliber rimfire
rounds, but this is changing as the popularity of .17 HMR rifles gathers momentum. 17 HMR
rifles and ammo have continued to sell briskly. It may be interesting to note that large retailer
Wal-Mart sells CCI .17 HMR in some of their suburban locations.
Following the success of the .17 HMR, the .17 Hornady Mach 2, was introduced in early
2004. The .17 HM2 is based on the .22 LR case necked down to .17 caliber using the same
bullet as the HMR but at a velocity of approximately 2,100 feet per second in the 17-grain polymer
tip loading.
A growing number of companies offer .17 HMR ammunition. CCI Ammunition loads all of the
.17 HMR ammunition for the CCI, Federal Cartridge, Hornady, and Remington brands. However, the
ammunition is loaded with different bullets to different specifications. Ammunition is
also available from Winchester, PMC and Sellier & Bellot.
Citing safety concerns about the round's use in semi-automatic firearms, Remington issued
a product safety warning and recall notice. Comparison with .22 LR Ammunition
Advantages Higher velocity: 2350-2550fps compared to
the popular ≈1255fps .22LR High Velocity. Flatter trajectory
Longer range As the round is faster there is less chance
of ricochet due to bullet 'break up' at shorter ranges
Disadvantages More expensive.
Overly destructive at close range for small game.
The cartridge is appreciably louder. Comparison with .22 WMR Ammunition
Advantages Faster flight: 2350-2550fps compared to the
Hornady 2200fps 22Wmr 30gr rounds Flatter trajectory
Longer range. Bullets expand better especially at longer ranges e.g. 150 yards
As the round is faster there is less chance of ricochet due to bullet 'break up' at shorter
ranges Disadvantages
Less kinetic energy Slightly more expensive
See also 4 mm caliber
Table of handgun and rifle cartridges 4.5×26mm MKR
References
External links Varmint Al's Field Testing the .17 HMR