Unsized, unlubed bullets are sold to those who wish to experiment. For example, I might buy .360 diameter bullets so that I can reduce some to .359, some to .358. and some to .357. With these different sizes I can experiment. I have 3 tools called lubrisizers that can reduce diameters and lube at the same time. Nobody and I mean nobody buys unsized and unlubed bullets to save money.
A myth in shooting and loading cast bullets is that harder means less leading. Cast bullets bought from commercial casters as a rule are too hard and are lubed with a super stiff lube designed to run through automated machines and also not to melt in summer heat. A too hard bullet does not upset or obturate meaning that it enters the barrel at a too small diameter. Hot gases then pass by the bullet and cause smears to stick to the barrel. Many of the stiff and hard type lubes are not adequate.
Missouri Bullets has good products. Buying and shooting cowboy bullets will provide the better and softer composition which will obturate.
I learned all this stuff the hard way by beating my head against the wall as I read and studied and experimented. It's my favorite topic.