美国MSAR公司STG556步枪的原型是奥地利斯太尔公司AUG A1突击步枪。STG556步枪在继承了原型枪的基本结构和外观形状的基础上添加了一些AR15系步枪的元素:如弹匣卡笋上方的空仓挂机解脱杆改成了类似AR15系的样式;机匣左侧的抛壳窗前方设有AR1S系步枪特有的辅助推机柄,只不过该推机柄并不是直接作用在枪机上,而是作用在拉机柄与枪机的 The prototype of the US MSAR STG556 rifle is Austrian Steyr AUG A1 assault rifle. STG556 rifle in the inheritance of the basic structure of the prototype gun and appearance based on the shape of the AR15-based rifle added some elements: such as magazine card shoots above the hangar hang up the bar into a similar AR15-like style; the left side of the casing In front of the throwing shell window, AR1S rifle-specific auxiliary push handle is provided, except that the push handle does not directly act on the bolt but acts on the handle and the bolt