If 900 BBs isn't enough for you, you're doing it wrong. :blink:
The one's I linked
are cheap, and
are good. In fact, for what they are, they're very cheap. I rarely see other's using them and I cry inside.
They work flawlessly in my G&G - though you loose 4 bbs on reloads it's no big deal.
Anyhoo, this should suit you just right:
http://www.taiwangun.com/en/electronic-winding-magazine-and-box-magazines/800rd-electric-dual-magazine-for-m4-m16-rechargeable-black-battleaxe?from=listing&campaign-id=19
Or
http://www.taiwangun.com/en/magazynki-aeg-hi-cap-2/m4-series-hi-cap-magazine-for-400-bb-s-cm?from=listing&campaign-id=22
I have a Battleaxe electric winding mag and it works great, I hate it for the same reasons I expect(I've never used another hicap) I would hate using hi-caps - no stealth, no panic reloads, no fun.
From:
http://www.taiwangun.com/en/magazines
UKARA is not required.