on a "round-per-shell" basis such that for every pellet fired, a shell casing is ejected and the cap is fired providing a realistic sound and smoke effect. Since its debut, the only hybrid guns seen on the market are TOP M4A1, as well as M1 Garand, Kar98, and other rifle models. These guns are the least common type of gun on the market today and are generally used by collectors and re-enactors rather than skirmishers. Gas blowback hybrid operation: Hybrid gas blowback airsoft guns are quite similar with hybrid AEGs and their operations are similar with ordinary gas blowback airsoft guns. A single 6 mm pellet is still loaded to a shell casing. Then it is placed into a magazine. The airsoft replica itself also has a tank for compressed gas as propellant (such as green gas). So as the slide/bolt is pulled back, it loads a shell into the chamber. As the trigger is pulled, it releases a small burst of propellant and the pellet is forced out the barrel. Training weapons Airsoft gun manufacturer Systema Engineering (PTW) developed a line of airsoft guns and accessories intended for military and law enforcement training. These airsoft guns are made of aircraft-grade aluminum combined with stainless steel parts that gives strength, stability, weather protection, and easy maintenance. These training weapons offer a more realistic display of military weapons. Unfortunately they have been plagued by reliability problems and parts availability. They have also had models banned from the US for being capable of being converted into real firearms. Two manufactures, King Arms and KWA, came out with ATF-approved gas blowback AR-15 replicas that allowed for correct weapons tear down, manipulation and function that were designed for military use, but were also legal for US citizens to own. The King Arms model required upgrade parts out of the parts to give it reliability, though the KWA was plagued by a weak hop-up system, but otherwise reliable. In November 5, 2018, the United States Coast Guard, which has long used the .40 caliber SIG P229 as its duty sidearm, announced that it will acquire the SIG ProForce P229 CO2 airsoft pistol (which was then produced under brand licensing by French airsoft manufacturer CyberGun, before SIG later ceased external licensing and took over the production in early 2019) as its new training pistol to give cadets and guardsmen the ability to practice gun handling, conduct