Real Sword SVD Piston

So just recently got the real sword AEG SVD and it shot quite well until it stopped feeding. I don't know if this was because of the mag, low power battery (7.4 lipo, getting 9.6) or problems in the gear box.

So anyways I opened up the gun with my dad and we cleaned the inside of the gearbox and stuff like that, but then when we put it back together and tested it. It wouldn't shoot out any air. So, we opened it up again and we saw that the piston's teeth were stripped. It turns out, quote on quote, "The Real Sword SVD's piston is a P.O.S." :doh:

So we're going to have to replace that... Any suggestions? And the gun wasn't the most accurate thing in the world so do you guys suggest any simple upgrades for it? Also, what could the feeding problem be? I think my mags feed just fine, but I'm gonna get a hi-cap just to see if it feeds better and I'll get a 9.6 since I wanted to get that anyways.