I'm fairly new to the airsoft world and just picked up the black ops m4 cobra cqb on ebay for $60 free shipping. The fun didn't come with a buffer tube, stock, battery, or charger. I picked up a buffer tube for $11 and have an extra magpul stock from my ar15. First question is will my magpul stock work with the airsoft buffer tube? My second question is what size and type of battery should I invest in? Right now I play at a local arena that limits all guns to 300fps and will be playing some woodland in the near future where I would like a higher fps. I have read quite a bit about the batteries and connectors so no need to dumb it down much. On another note, I'm curious if anyone has ever modded a rifle to use 12v power tool batteries? I've got some milwaukee 12v batters that are very compact and run 3000 mah. Thanks for looking!