First, that’s a great question.
Second, just asking it indicates that you are possibly the awesomest girlfriend ever and he should immediately stop the movie and make passionate lo - oh sorry.
Third, I was Army in another country but can confirm for my part that it was “always” correct to keep a muzzle down unless the rifle is over the shoulder and the barrel at 90 degrees. The reason I say this is that in archival WWI and WWII footage they seem to carry their weapons as we do.
Yep.