So here is what I did: I used the wrong powder (RL-19 instead of RL-15) while loading 168 gr SMK for my .308. I'm not sure when I made the switch, but the most I loaded was 42 grains of RL-19 and the least would have been 40.5 grains. Are those safe to fire, or do I have to destroy all the powder and start over?

The irony is that I had just read an article about how easy it is to make mistakes with powder, and I was actually sitting there thinking that everyone else in the world must be real dense if they can't tell the difference between two different cans of powder. While thinking these thoughts I set the RL-15 down on my left and unwittingly took the can of RL-19 from my right and started loading with it. (I use a scoop to load, but I weigh each charge.)

The biggest mistake is assuming that you are so much smarter and more observant than everybody else. Pride goeth before the fall. This is a lesson learned.