What would you like to know?
Tanaka M700 are all the same internally and on all version the only think that changes is the stock and the outer barrel.
The M40 released in 2 versions one with polymer and one with wood stock.
You'll probably will hear about pre ban and post ban versions... The pre and post ban rifles are exactly the same except the bolt.
On the pre ban rifles the bolt is equipped with an unrestricted nozzle and PCS(Power Control System).
The PSC is nothing weird is simply a bolt that regulates the gas flow, you can adjust the fps at field limits but most users simply leave it max setting so it's useless, besides you can do that with far more accuracy with an external rig.
This is the PCS bolt
This is the restricted nozzle
The unrestricted is this..
The standard piece that brakes is the part 91 the hop up housing.
There are metal housings available.
The most common upgrade parts are the Hop Up Housing (Part 91), the VSR conversion hop up chambers ( you'll also need and a VSR cut barrel), 9ball VSR purple (hard) bucking, the power pack (durability upgrade, it didn't fit in both my M700's!! ), power bolt (you'll also need to mod your bolt handle and it doesn't work with VSR conversion kit with out mod), steel sear.
IMO Tanaka's are way overrated and over priced, everything is made by cheap pot metal that will fail sooner or later.
The light bolt pull is a nice feature as and the high fps but it's incredibly inconsistent and there are no spare parts like spare trigger springs and stuff like that.
If you need anything else feel free to ask.