Hi I'm new to forums so forgive me if I'm not posting in the right place etc... just out of curiosity is it possible to convert an Ics nbb m4a1 to blowback? if they both have split gearboxes I know I would probably have to use the charging handle for an ebb and swap out the fake bolt. would it be possible to remove the top nbb gearbox and put in a ebb top end along with charging handle, bolt plate etc.. would it fit on a Ics m4a1 with metal upper receiver which is compatible with the Cxp Series if not why ? And if so what would need to be done ( minor mods like filing for example) not to be rude but the reason why is just general curiosity. Any help or advice would be much appreciated thanks in advance.