HK has a history of innovation in firearms, such as the use of polymers in weapon designs and the use of an integral rail for flashlights on handguns. HK also developed modern polygonal rifling, noted for its high accuracy, increased muzzle velocity and barrel life. Not all its technologically ambitious designs have become commercially successful products (for instance, the advanced but now abandoned G11 military rifle, which fired caseless high-velocity ammunition). In its extensive product range, HK has used the following operating systems for small arms: blowback operation, short-recoil, roller-delayed blowback, gas-delayed blowback, and gas operation (via Short-stroke piston).