A-derp.
Got a stock on it, finally. But it'll be temp unless I can fix up some 'mistakes' i've made whilst dremeling and sanding, lol.
Aaanyway, the whole cycling thing seems to be an on/off occurance. Just started firing it with this stock fitted and it seems to be fine... Hm, I'm curious, would overtightening the screws have anything to do with it possibly? I still have that damn bolt-lock problem and the mag is seated properly.