without causing undue alarm. The .22 LR has also seen limited usage by police and military snipers. Its main advantage in this role is its low noise, but it is usually limited to urban operations because of its short range. One study suggests a single head/torso shot suffices, more often than not. See summary table of results from Greg Ellifritz’s Stopping Power study. The Israeli military used a suppressed .22 LR rifle in the 1990s for riot control and to "eliminate disturbing dogs prior to operations", though it is now used less often as it has been shown to be more lethal than previously suspected. Some other examples include the use of suppressed High Standard HDM pistols by the American OSS, which was the predecessor organization of the CIA. Francis Gary Powers was issued a suppressed High Standard for the flight in which he was shot down. Suppressed Ruger MK II pistols were used by the US Navy SEALs in the 1990s. Cartridge dimensions .22 long rifle maximum C.I.P. cartridge dimensions. All sizes in millimetres (mm). The common rifling twist rate for this cartridge is 406 mm (1:16 in), six grooves, land width = 2.16 mm, Ø lands = 5.38 mm, Ø grooves = 5.58 mm. According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the .22 long rifle can handle up to Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. Because the .22 long rifle round commonly uses a heeled lead or lightly plated bullet, the nominal bullet diameter is larger than the nominal bore diameter to prevent excessive lead fouling that can occur when shooting lead bullets that are the same or slightly smaller than the groove diameter. SAAMI specifies a nominal bullet diameter of 0.2255 with a tolerance of -0.004, while the specified bore diameter is 0.222. In practice, 0.224 or slightly larger bullets are common, with barrel groove diameters commonly around 0.223. Muzzle velocity (nominal) lead: .22 LR subsonic copper plated lead: .22 LR high velocity copper plated lead: .22 LR hyper-velocity CCI Stinger Note: actual velocities are dependent on many factors, such as barrel length of a given firearm and manufacturer of a given batch of ammunition, and will vary widely in practice. The above velocities are typical.