It is safe, but you might be surprised how load it is. Do it when wife is not home.
When I make dummy rounds I remove the decapper pin/expander from the sizing die and neck size. this will give max neck tension, so bullets do not come loose. i also run some Loctite in the case neck, to help hold the bullet.
The dangerous part of dummy rounds is that one day a real round might get added to the mix. That can get real loud. Not dangerous though, because we all practice safe muzzle control, right??
right??