as Phil said, scotch tape. You have a belted mag, so your head space is in that quarter inch between the belt and case head. You get more then 2 pieces of tape in there and it closes you found a problem.
As to Nickle plate brass, I was told the do that to seconds to make it usable. Nickle dose not like being worked a lot and will crack and peel with to much body work.
Is your brass all the same brand? Mixed can cause spikes also.