[hattrick]

The japan version is the EXACT same as the taiwan version, the difference is their quality control.

Half of the said gun are sent to a shop where they are taken apart and made sure to be good quality then stamped with the 'jasg' Making them -japan versions- and costing a little more. (reduce the chance of receaving a lemon aka a dud)

The g&p custom is just with a pre-installed metal slide & barrel (making it able to handle propane aka green gas aka top gas)
As said before the kickback is pretty strong and, even then i would recomend an upgraded recoil spring to reduce the chance of blowing out the back of the lower frame.

The TM usp is an electric gun, NOT a gas gun.

As i said before, the trigger is damn near impossable to replace. (assuming you live in canada)

If you're located in the states please mention this, it'll make it a little easier to answer your questions. (since the USA has much better availablity of parts)

-alex