More than likely a dumb question, and I already have my thoughts, but wanted to see what others are doing. Hornady #9 has 3 different sections for 223/5.56 data: 223 Remington (1-12" twist), 223 Remington service rifle (1-9" twist), and 5.56 Nato (1-7" twist). My rifle is an AR, it has a 1-8" twist, and a Wylde chamber (gun is stamped 5.56mm). I was initially going with the service rifle data, but looking at the 5.56 nato data it gets closer to what the VihtaVuori website load data looks like (as well as some of the other powder manufacturer's website listings) - I guess as long as one starts at the lowest charge and works up carefully, it will all be similar in the end...