M4 Gearbox question
I am new to AEG and what to build an M4 and wondering which gearbox to use (Systema, G&P, Marui etc)
My aim is for the gun to be as powerful as possible. Would be grateful if anyone could advise if I should buy a Marui or G&P gearbox and modify or just simply buy a systema magmun gearbox? Your advise is highly appreciated - thanks all!