During the 1960s, Heckler & Koch perfected the famous polygonal profile barrel technology. Conventional lands-and-grooves rifling allow propellant gasses to escape around the front of the bullet as it is fired from the barrel muzzle. A polygonal bore profile effectively seals propellant gases behind the bullet—increasing bullet velocity. An added benefit of a polygonal barrel is its resistance to wear. A polygonal barrel will normally outlast a conventional “lands-and-grooves” barrel by thousands of rounds. Polygonal barrels were one of the many radical design elements used on the HK P7 series pistol and this same breakthrough technology is present on all current HK handguns.