I attended a Combat/Police training school.  We had stages set up similar to IDPA scenarios.   One big difference was that when we retreated up range from one position of cover to another, we turned and held the gun in front of us pointed down at the ground at around a 30 degree angle.   Those of us who shoot IDPA or IPSC competition felt very strange since we have been running up range with our gun arm sticking out behind us in a very unnatural position so as not to break the 180.   After a while the 180 turn with the downward muzzle felt very safe and natural.  Different strokes.  Bill