RE: Winchester M70 Saftey Trick...
I use the same practice, I store all of my rifles in this state, it takes the pressure off of the firing pin and spring. Some rifles can be damaged by dry firing, if you plan on dry firing for practice (called "snapping in") you should purchase a "snap cap", it is either a solid rubber/plastic or plastic/metal shell with a spring loaded "primer". They fit into your chamber and provide resistance for the firing pin.