parents and my interests

[green]

so im very into guns and knives and all things military. My dad is an officer in the australian air force and he has sort of influenced me. Heres the problem. I love shooting. I would love to take up shooting as a sport with my dad so that we can spend a bit more time together. I would help pay for the equipment because it is fairly expensive. But my mum would never let me do it. She is always giving me a hard time about knives. If im on my laptop looking a knife website she gets sorta angry and asks me why i cant be like a normal kid. I dont see what the problem is. I dont screw around with them, I dont take them to school, I dont flash em around. Why is it such a bad thing that I like knives and guns.
So how do you guys think i could convince my mum to let me collect my knives and to start sport shooting?