A .30 or .50 caliber automatic belt-fed, air-cooled or water-cooled machine gun capable of firing ammunition at a rate of more than 500 rounds per minute.是什么意思_A .30 or .50 caliber automatic belt-fed, air-cooled or water-cooled machine gun capable of firing ammunition at a rate of more than 500 rounds per minute.在线翻译_英语_读音_用法_例句