.17 HM2
Encyclopedia
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
"Stinger" case, necked down to .17 caliber
(4.5 mm) and using a bullet weighing less than half what typical .22 Long Rifle bullets weigh.
s more difficult, as virtually all are blowback
designs that are sensitive to pressure changes. Kits for the Ruger 10/22
and AR-15 platform have appeared, and they replace the factory bolt or bolt handle with a heavier one to increase the bolt mass and compensate for the higher pressure. 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.
Cartridge (firearms)
A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...
introduced in 2004 by the ammunition
Ammunition
Ammunition is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...
manufacturer Hornady
Hornady
Hornady Manufacturing Company is an American manufacturer of ammunition and handloading components, based in Grand Island, Nebraska.The company was founded by Joyce Hornady in 1949 and is currently run by his son Steve Hornady who took over after his father's death in a plane crash in 1981.Hornady...
, following the successful launch in 2002 of the .17 HMR
.17 HMR
.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, and it is more costly to shoot than traditional .22...
. The .17 HM2 is based on the .22 Long Rifle
.22 Long Rifle
The .22 Long Rifle rimfire cartridge is a long established variety of ammunition, and in terms of units sold is still by far the most common in the world today. The cartridge is often referred to simply as .22 LR and various rifles, pistols, revolvers, and even some smoothbore shotguns have...
"Stinger" case, necked down to .17 caliber
Caliber
In guns including firearms, caliber or calibre is the approximate internal diameter of the barrel in relation to the diameter of the projectile used in it....
(4.5 mm) and using a bullet weighing less than half what typical .22 Long Rifle bullets weigh.
Performance
The ultralight bullet is a key part of achieving the very-high velocity for a rimfire round. It weighs only 17 grains (1.10 g) vs 30-40 grains (1.94-2.59 g) for typical .22 LR bullets. The .17 HM2 may or may not live up to its "Mach 2" name, depending on geographic location and conditions, with velocities out of a rifle of 2100 ft/s (640 m/s). The velocity is nearly double that of a standard .22 LR, which results in a much flatter trajectory out to the 175 yards (160 m) effective range of the cartridge.Costs
The tiny .17 caliber jacketed bullet is much more difficult to manufacture than the copper-coated lead .22 LR bullets, and that is reflected in the cost--typically twice that of inexpensive .22 Long Rifle ammunition. The price is still less than any surplus centerfire ammunition, and less than the more powerful .17 HMR. The high priced bullet used in the .17 HM2 does have its advantages including accuracy.Converting rifles
Since the .17 HM2 is based on the .22 Long Rifle, converting most firearms chambered in .22 Long Rifle to .17 HM2 requires only a barrel change. The higher pressures makes conversion of semi-automatic firearmSemi-automatic firearm
A semi-automatic, or self-loading firearm is a weapon which performs all steps necessary to prepare the weapon to fire again after firing—assuming cartridges remain in the weapon's feed device or magazine...
s more difficult, as virtually all are blowback
Blowback (arms)
Blowback is a system of operation for self-loading firearms that obtains energy from the motion of the cartridge case as it is pushed to the rear by expanding gases created by the ignition of the propellant charge....
designs that are sensitive to pressure changes. Kits for the Ruger 10/22
Ruger 10/22
The Ruger 10/22 is a semi-automatic rimfire rifle chambered in .22 Long Rifle. It has a removable 10-round rotary magazine which allows the magazine to fit flush with the bottom of the stock. Higher capacity magazines are also available...
and AR-15 platform have appeared, and they replace the factory bolt or bolt handle with a heavier one to increase the bolt mass and compensate for the higher pressure. 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.