We had them on our weapons (M16A1s) in basic training in 1974. Yep, they were loose and often came undone, usually while marching! More than one poor recruit had it come loose and hit the ground. They would have to hold it over their head with one hand, and grab their "JUnk" with the other hand. They had to double time around the formation (while it was moving) shouting "This is my weapon (hiking weapon up higher), this is my gun (grabbing your stuff), This is for killing, and this is for fun!"