When it comes to this sport, there's no such thing as a dumb question. If there is, I've asked it.
I cast (casted?) a bunch of roundballs a few years ago and some of them weren't perfectly round, but I shot them anyways. Well, I had two double chamber fires, in two different guns (both .36 caliber) and in both guns the caps were unfired. The only reason I can think why it happened is that the irregular shape of the balls allowed a spark to enter the next chamber. Both times, it was no big deal - a little extra pop, some more smoke, but I'm careful now; wrinkled balls don't get shot.
Also, I use a Lee electric bottom pour melter, which has been great, but a few weeks ago I decided to take it all apart to clean it. Good thing I did - the heating coils that wrap around the pot were all cracked and split, and probably dangerous. $14 to replace the coils but I think I might go back to using a melting pot.