Mach Sakai has already gun over Maruzen M870 airsoft shotguns and for this video, he checks out the Maruzen M870 Extension Custom Black Version (EX BV). The M870 composite stock shotgun is a popular and realistic airsoft gun that is often used by law enforcement agencies around the world. It can hold up to six shells, which eject with every pump. Each shell can hold one to five BBs, but the more BBs per shell, the less power the gun will have. For optimal performance, it is recommended to load three BBs per shell. The M870 composite stock shotgun is not as powerful as some other airsoft guns, but it is very realistic and operates on HFC134a gas power.