The military's weapons do not use springs on the firing pin though. Most Civi rifles do for some reason. Back when I was in the Army I was told that dry firing my assigned weapon * A M-16A2* was not going to damage it. I spoke up, "drill Sargent, I have always been told that dry firing my rifles at home would damage the firing pin, why not this rifle?" They said the Army specified extra thick firing pins because they were going to be dry fired alot and that civi guns were not always "up to spec" so I take that to mean my civi rifles could be built with thinner weaker parts to include the firing pin.
To the OP: Once could do no damage to any rifle, if you decide to make a habit of it their are shells specifically designed for dry firing use that will protect the firearm. They are a hard plastic with a rubber primer area.
I had been told for years that using a spent cartrige was just the same and in so doing was saving money * a big thing around home* but it is not true. Only the dummy cartridges can do this.

Thanks for reading,
Ole Switchback XT runnin his mouth again!!!