It's a little rough at the moment (WIP), but I used an AEG PMAG shell for my WE GBB mag.
Grafted part of another broken PMAG on top to get it to fit and engage the mag catch properly.
Dummy rounds are from a free download from Intrudershop for a WE G36 mag, printed on paper, trimmed and slipped into place.
Fires fine and the bolt locks back on empty every time .
