went with the G&P complete gearbox from EHA. had no problem with fitment. actually took more time getting the reciever together with all the pins and what not. super tight tolerences. The trigger pin actually sticks out .5 mm cause im too scared to force it thru in fear of warping the body. shoots 380 fps w/ .25's. running a prommy neo chamber, km head inner barrel and pdi w hold bucking. waiting for my chrono to come in before i cut the spring down a bit to get to down to 350.
buffer tube fitment was fine. only problem I had was after snugging the screw from the inside of the stock tu