Perchased piercing gun on eBay and mum found out?!?

Be mature and have a talk with your mum.

In the mean time, here's some information about why piercing guns are a really bad idea http://www.safepiercing.org/piercing/faq/#guns

Hopefully after you've read it you can appologise for not realising how harmful self piercing and and piercing guns are. Explain why you got it, if it's for a certain piercing maybe she'll let you get it, if not you'll have to wait until you're legally able to go to a legitimate piercer who has had training and uses needles for all piercings.

Ride out the storm my friend. Just make sure you look suitably chastised and agree with anything she says, and apologize.

Also, self piercing is a really bad idea. Far better to spend the money on a pro job. I've done both (when I was younger) and I've had 100% less problems with professionally done piercings.

have fun with your mum :)

i would ask her which ear and how many times she wants piercing

It's really dangerous, what ever you do DON'T pierce your cartridge with it!