I think that the concern over dirt or mud in the muzzle was probably addressed by the Mauser Bros and others who made weapons for use in war years ago..
Cleaning rod attached to the rifle and cleaning kit given the soldiers...and some training on where to and not to put the rifle's muzzle..:0..and some physical training so when they had to hit the ground, their weapon was protected best they could.
Probably didn't help all the time..Not many wartime stats on damage caused by mud in the barrels from WWl or WWll etc..:)
The tape is a cheap insurance for those who fall down alot or cannot keep track of their rifle when traveling in rough country..:) I personally don't and never needed to but some do..:) Jim
