Gad! I'm really surprised that you weren't hurt any worse than you were!
Honestly, I've never done any reduced power rifle loads -- yet. I can see the day, in the not so distant future, where I will be doing so. I'll keep that in mind.
That said, I'm all too familiar with the hazards of double (or triple) charging. I do a lot of handgun reloading, and of that I do a LOT of .38 Spl using low volume, high energy powders such as HP-38 and Bullseye. Knock on wood, but I've never double charged yet, even though with such low volume powders you really can't tell if you've double charged even by visual inspection. My SOP is that if I am interrupted on any one case, or have any question about it, the best practice is to dump the case and start over on it. Better safe than sorry.