A loader who stopped after 20 rounds and is selling his equipment?
A loader who did not seat his primers properly? Maybe did not measure the powder correctly, either? Or read the load recipe correctly?
There was a thread from a .45 ACP shooter who had scared himself out of reloading any more after he blew up his gun. He was using one of the three "Clays" powders. (I suspect he used the wrong one.)
I encouraged him to post back the exact powder he used, but he has apparantly left the forum.
The coincidence is too suspicious for me.
(not the same guy, as the O.P. on this thread mentions that he got a different manufacturer's equipment for Christmas. But they could be related to each other.)
Pull those bullets, dump the powder in the cases (it makes decent fertilizer when diluted - full of nitrogen, you know). Look very carefully at the label(s) of any powder he sold you (consider disposing of it if it is at all suspicious) and proceed from there.