Cajun;
I think over time you will discover, and agree that casting good bullets is really an art form and as such everyone will have their own techniques.
I cast in my shop so I have a couple of different routines that I employ to get consistent bullets depending on the time of Year/weather. You will spend many hours trying to find what works the best 'for you'. As your experience grows you will start to learn what works for you and what doesn't. The key is finding a technique that shows promise and refine it. After many many thousands of bullets, we all still find tiny changes that can make big differences in what would seem a common routine.
There are some youtube videos that show the basic routine but there are so many variables that can change a bullet, you have to learn them all.
Basics that will change a bullet;
1 Melt Temp
2 Mold Temp
3 Mix i.e 16/1 25/1 etc.
4 Weather
5 Mold condition
6 Pouring time
7 Ladle pressure on sprue plate
8 Length of time of cycle for pouring a bullet
9 Sprue plate tension
10 Pouring 'technique'
And on and on and on. The causes of change can seem endless sometimes.
Those of us that have poured many bullets sometimes forget the time we have spent refining 'our' method, as well as the minor change we subconsciously make as we pour. It's all based on hours of experience and the only way to get that is cast and cast and cast some more.
Yes 1/2 a grain is very possible. I sometimes on a good day can cast the first 3 or 4 and get into a rhythm and cast 60 that are within 2 tenths.
60 is my base for a number to cast. That's about an hour +/-. That's my limit to get good bullets.
Cast a lot. Enjoy the time, it will become therapy and allow many hours to think about many things.
Enjoy
Cary