The .17 Hornady Mach 2, or .17 HM2, is a
rimfire cartridge introduced in 2004 by the
ammunition
Ammunition (informally ammo) is the material fired, scattered, dropped, or detonated from any weapon or weapon system. Ammunition is both expendable weapons (e.g., bombs, missiles, grenades, land mines) and the component parts of other weap ...
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
In guns, particularly firearms, caliber (or calibre; sometimes abbreviated as "cal") is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore ma ...
(4.5 mm) and using a bullet weighing less than half the weight of a typical .22 Long Rifle bullet.
Performance
The weight of the bullet is a key part of achieving a very high velocity for a rimfire round. It weighs only 17 grains (1.10 g) vs 30-40 grains (1.94-2.59 g) of a typical .22 LR bullet. 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 2,100 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 its 175-yard (160 m) effective range.
Converting rifles
Since the .17 HM2 is based on the .22 LR, converting most bolt action firearms chambered in .22 LR to .17 HM2 requires only a barrel change. The higher pressure makes conversion of
semi-automatic firearm
A semi-automatic firearm, also called a self-loading or autoloading firearm ( fully automatic and selective fire firearms are also variations on self-loading firearms), is a repeating firearm whose action mechanism ''automatically'' loads a fo ...
s more difficult, as virtually all are
blowback designs that are sensitive to pressure changes. Conversion kits 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.
See also
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.17 PMC/Aguila
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List of handgun cartridges
List of handgun cartridges, approximately in order of increasing caliber.
Table of handgun cartridges
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, -
! Cartridge name , , Bulletdiameter , , Caselength , , Cartridgelength , , Type , ...
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List of rifle cartridges
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List of rimfire cartridges
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Table of handgun and rifle cartridges
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4 mm caliber
References
Further reading
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External links
EleyCCI
{{DEFAULTSORT:17 HM2
Pistol and rifle cartridges
Rimfire cartridges
Weapons and ammunition introduced in 2004