Series (OLCMSS) had 800 people attend at George Air Force Base in Victorville, California. American Mil-sim, Black Sheep, and Ballahack also host large games. The attraction of the larger games is due to the intensity and variety in equipment that is used, ranging from small arms to armored vehicles. In many countries, every airsoft gun owner and active enthusiast must be affiliated with an accredited airsoft association or federation. Most airsoft players host games at a registered field where combat situations are simulated using airsoft weaponry like replica pistols, submachine guns, carbines/assault rifles, DMRs/sniper rifles, light machine guns, grenades and landmines. Great variety and profusion of militaria is usually used. Historical reenactment of famous war situations is another favorite of many airsoft players and clubs. In addition, a number of companies such as Systema Engineering and Celsius Technology manufacture ultra-realistic high-velocity airsoft rifles designed specifically for the police and military for non-lethal training purposes. People today can also use it as props for film making. Types Spring-powered Spring-powered airsoft guns (or "air-cocking guns" as called by Tokyo Marui) are single-shot devices that use the elastic potential energy stored within a compressed coil spring to drive a piston air pump, which is released upon trigger-pull and rapidly pressurizes the air within the pump cylinder to in turn "blow" pellets down the gun barrel. These guns are almost identical (though simplified and underpowered) in design to spring-piston air guns and have the same operating principles. The user must manually recompress the spring under stress prior to each shot, typically by pulling back the slide (pistols), bolt handle (rifles) or forend pump (shotguns) on the weapon, which cocks and readies the gun. Because of this, spring guns are incapable of automatic or semi-automatic firing by design. Spring-powered airsoft guns are generally not as powerful as gas-powered ones, but are more powerful than electric airsoft guns because stiffer springs can often be used without the worry of overloading any motor-gearbox, although some spring shotguns and bolt-action rifles can be very powerful with muzzle velocities up to . Spring guns are generally inexpensive (except the high-power sniper rifles and shotguns), and may not last long (depending on the build quality) due to the tension exerted on the gun parts by the recoiling of a powerful spring. However, many spring guns can be modified and upgraded to last longer and shoot more powerfully. While most electric