How do i convince my mom to let me buy an airsoft gun?

I am 12 and I want to buy an airsoft gun(an M41K), but my mom thinks they are violent and dangerous. How do i convince her to let me buy one with my own money? I don't think my dad will be much of a problem, cuz he used one when he was a kid a lot, and he had a sharp throwing star.
Update: I can" go out an buy one becuase I need a credit card. Which I don't have. I could steal it but she woul get the bill.
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