Over the last thirty years I attended a couple dozen shooting courses through my department or in-service training sessions using guest instructors where drawing, holstering, shooting and reloading were all required to pass. Not ONCE did we ever address a shoulder holster and how to properly use it. Matter of fact, I never heard of any agency that did.
That may be the reason I never owned or even wanted one.
That may be the reason I never owned or even wanted one.