There are some serious errors in the script of the video. The gun shown is actually a Mark I, and one of the distinguishing features is the safety catch - which is NOT a winter trigger! As well as the major shortcoming of the magazine housing preventing chamber inspection, it makes shooting prone almost certain to result in a blocked exit port from a mixture of earth and empty cases.

Quite clearly the S&W designers had no experience of field use of anything except revolvers.

Peter