When I hunt, I just hold my thumb over the end of the barrel to keep the bullet from coming out.
Seriously though, I have heard of people doing what is descibed here and didn't think it to be a problem. I was also thinking that the firing pin was not protruding from the bolt body when it was at rest. I never tested it. I thought is was something like an automatic pistol that had a second spring pushing the pin back out of the chamber after firing. I'm sure a little research will prove one way or the other but if the firing pin is able to touch the primer with the bolt closed, I would not carry a rifle in that condition. I'm off to look for bolt schematics.
Upon further review, I think it would be a bad choice of how to carry a rifle. 
Yes, it removes the potential energy from the bolt but it leaves the live round sitting on top of an exposed firing pin. enough of a bump to dimple the primer and it could be an accidental discharge. I've always trusted safeties and will continue to do so. In order to completely disable a loaded rifle from firing, I guess one must leave the bolt handle up.
Safe hunting to all!
