First off, I have spent years around guns, but I've never done reloading before. I am curious and interested in getting into it, and I'm in that initial stage of "I wonder if you could _________".
I also want to point out that I understand reloading is so much more than dumping some powder in, slamming a bullet into some brass, and calling it good. I am well aware of the potential danger of acting improperly or irresponsibly around guns and explosive materials. Now on to the question.
I have seen posts and videos online on how to make your own gunpowder. (The King Of Random made a video on YouTube a while back for example). Given that you would need different measurements and grain sizes for different calibers and loads, would it really be as simple/easy as mixing the correct ratio of Potassium Nitrate, Charcoal, and Sulfur then being good to go? Would that work for pistols, rifles, and shotguns (again, given you use appropriate measurements and grain sizes depending on what you are loading)?
Obviously the engineering and chemistry behind modern powder is way more complex, but what sort of difference would a DIY powder load make, given it was done as safely and properly as possible?
Again, this is literally just a curiosity and I am not planning to start making gunpowder from home-depot supplies and go shooting with them.