The thinking is that the PDX round with discs and BB's gives me an excellent chance for a hit with the first round, and if it doesn't stop the person, then the 410 buckshot will, as it puts out 4 .36 caliber balls.
That gives a pretty chance for a hit and a stop. I don't consider the 1st round a waste, because it would very likely stop a person, if it hits them in the right place. The .45's are for a longer distance if needed. That is my theory. Others load differently. I have never had a misfire with any rounds. I don't worry about a jam, or having to clear a round.