My biggest screw up happened yesterday. I had loaded some 140 accubonds for my both my 7-08 and my 280 AI. I'd shoot a group with one, set it down to let the barrel cool and shoot the other one. Broke the rule about not having 2 different boxes open on the bench at the same time.
This is what a 7-08 case looks like after its fired through a 280 Ackley

Funny thing is I actually hit an 8" steel gong at 300 yards. Almost no recoil but the velocity had to have been pretty good to be that close at 300.