BTW - as a state-certified firearm safety instructor, I first noticed students using the 'muzzle toward the ground' carry after Desert Storm, when returning vets, trained on military weaponry, brought the practice with them.
That carry works with a pistol-gripped assault weapon - especially when your next target is likely to be on the ground ahead of you. But in the civilian hunting field it is dangerous, especially around gun dogs, and it took some re-education to get those muzzles up in the air where they belong!
Jack,
It has nothing to do with "pistol gripped assult weapons" in that case. With a rifle an accidental discharge with the rifle muzzle in an elevated position the bullet could travel for miles! I know of ranges where if they catch you closing the bolt on a rifle with the muzzle elevated you MIGHT get ONE warning then you will be asked to leave.
I was taught you had to be extra careful carrying a gun muzzle up because if you stumble or fall it's hard to control the muzzle.
BTW I am a certified 4-H rifle instructor, the training I received from 4-H made me eligible to be an NRA certified instructor.
Sam