The KJW M700 is a clone of the Tanaka M700, so many upgrades available for the Tanaka will fit the KJW.
A word of warning - the weakest part of the KJW is actually the mags - they overpressurize easily if you use propane in them, and when they do that, they actually warp the flimsy block of metal inside the mag that acts as the gas chamber. DO NOT leave your mags fully pressurized with propane and sitting out in the sun or you will ruin the mags (which are almost $100 each shipped to Canada....ouch). I would also recommend replacing the original plastic chamber with an aluminum one...it's right where the barrel and frame connect and is notoriously prone to cracking.
As a side note, some excellent mods for these guns include adding a longer aftermarket nozzle, and buying a mag upgrade kit that will prevent the overpressurization issue - I would recommend replacing the stock mag internals with the unit from Caliber (
http://www.armamentia.com/front/php/...php?cate_no=33), other parts are available from King Arms, G&G, and Creation.
Illusion has an excellent thread in this forum about his buildup of his Tanaka M700 AICS, which internally is very similar to the KJW M700. I suggest you read the entire thing, although it really starts to get good around page 6.
http://www.airsoftcanada.com/showthr...ht=tanaka+AICS
Here's a good guide to get you started:
http://www.airsoftforum.com/board/Ta...de-t97342.html