There is definitely a learning curve.

I loaded 200 9mm this morning. Took a break, and did a painful 90x .357.

I wound up finding another range pick-up 9mm Win cases with a crimped primer. That trashed a primer and caused my first real train wreck. I segregated all of the Win brass and processed them separate. Unfortunately, over half of my 9mm brass is Win so it can be hard to find these problem children that got mixed in.

.357 posed a bigger problem. I am using my RCBS dies from probably the late 1970s. The size die and the seating die require too precise an entry into the die for progressive use. I can rotate a single round through the stations without a problem, but if the shell plate is fully loaded I start crushing case mouths.

I already resorted to a paper clip for the spent primer chute. It started hanging up and spent primers knew exactly where to go to jam up priming.