for the momentum equation, the energy values obtained may be less accurate. The value of the constant α is generally taken to lie between 1.25 and 1.75. It is mostly dependent upon the type of propellant used, but may depend slightly on other things such as the ratio of the length of the barrel to its radius. Muzzle devices can reduce the recoil impulse by altering the pattern of gas expansion. For instance, muzzle brakes primarily works by diverting some of the gas ejecta towards the sides, increasing the lateral blast intensity (hence louder and more concussive to the sides) but reducing the thrust from the forward-projection (thus less recoil), with some designs claiming up to 40-60% reduction in perceived recoil. Similarly, recoil compensators divert the gas ejecta mostly upwards to counteract the muzzle rise. However, suppressors work on a different principle, not by vectoring the gas expansion laterally but instead by modulating the forward speed of the gas expansion. By using internal baffles, the gas is made to travel through a convoluted path before eventually released outside at the front of the suppressor, thus dissipating its energy over a larger area and a longer time. This reduces both the intensity of the blast (thus lower loudness) and the recoil generated (as for the same impulse, force is inversely proportional to time). Detection Muzzle blasts can stir up significant dust clouds, especially from large-caliber guns when firing low and flat, which can be visible from distance and thus give away the gun's position, increasing the risk of inviting counter-fire. Preventive actions may consist of wetting the soil of the surrounding ground, having the muzzle brake vector the blast up and away from the ground, or covering the area around the muzzle with a tarpaulin to shroud down as much airborne dust as possible. Gunfire locators detect muzzle blast with microphones and triangulate the location where the shots were fired. These are commercially available, and have been installed by law enforcement agencies as remote sensors in many high-crime rate areas of urban centers. They can provide a fairly precise location of the source of a shot fired outdoors — 99% to within or better — and provide the data to police dispatchers within seconds of a firing. See also Suppressor Muzzle brake Recoil compensator Muzzle booster Muzzle shroud References Shock waves Firearm terminology