It happens. Women. It's alright, explain to her you are responsible for your own actions. But if your father and mother is paying for the house and food you live and eat from, you respect them. As others have stated, you can move out with a friend, but even trying to rent a place when you have airsoft is 10x worst than what your mom gives you.
Your mother just wants what is best for you. Do somethign to make her proud, then she can probably allow this stuff in the house.