V2/3 may work (hell it did for sid) but V6 gears DO NOT WORK Neither will the piston- the v6 gears are very slightly different to the acadamy gears, this means that the gears do fit but they lock in and dont turn. the academy gears seem okay for a stock tm spring(in all 30 minuites/300 rounds ive put through mine) but the MP5 FTK would seem the way to go for 328+/- fps
on guide slots: if the famas only has one then the piston is useless in an L85(well mine anyway) as the piston in the l85 has two guide slots with "wings" on the back end.