Finally caved and bought a Autobot speed loader, much easier for pews that don't have M4 mag privledge and require funky 3D printed adapters to load from.
The 600 mAH 11.1v BZ reccomends fits [barely] but I feel it's a little too much juice as it's very easy to have the sheer torque push the mag out and spill ammo everywhere, and with certain mags - namely the PTS EPM-Gs for G36 - I fear that it might be denting the rounds as it's putting a lot of pressure on them and it'd very much suck to have the lovely G36 Neg put together for me knacker itself due to a jam on it's first outing (still waiting on a few last minute details to be added to it before it's sent out)