I'm listening this classic army mp5 up on here but it's not quite boneyard..... I've stated to upgrade this mp5 with with all the usual stuff so it's got, double oring nozzle, double oring cylinder head, shs 14 tooth piston, standard piston head,tight boar barrel 6.02 I think, yellow maple leaf hop rubber with an omega nub, jefftron leviathan and a warhead motor and ended doing a short stroke mod to the gear's, it was running so fast until it broke the gear's and damaged the gearbox case, so I put a standard set of gears and replaced the gearbox with a one that I've got here and she shoots just fine ie on .28 it's doing + or - 292 fps, there is damaged to a cap that sits in the gun the holds the spring guide this was done by taken the gun apart so many times that is broke, but I did repair the with some high strength epoxy resin and it works just fine, so I've slow down the leviathan and it's only on semi, I do believe that it was because when it broke it was on full auto and shooting crazy fast ither way it needs to go to someone that has more time on there hands than what I've got, can send a video of it working right now, I bought a hpa set up lats night so that's why he up for sale £250 post and PayPal all in