You could get a TM mp5k, upgrade the moter. But then you would have to upgrade the battery and put it on the outside. You would also want the spring upgraded to 400 or u wont hit Shit . Meh so ur prob at 500 bucks there. Then spring another 100 for a double drum. 600 bucks. Meh, i would just then go with an AEX custom gun. Such as the Muskrat. But that has less range then most heavy machine guns, so blah.