For handloaders, it’s prudent to only use data from reputable sources. Most propellant and bullet manufacturers offer proven recipes in their pamphlets and manuals and, more recently, online. Concerning the latter, among the most useful websites that I consult is hodgdonreloading.com, and it was just made better. The new Reloading Data Center (RDC) has a much-improved-and intuitive-format, and it works better with smartphones and tablets. In addition to reloading recipes for rifle and pistol cartridges, and shotshells, there are also extras, such as basic reloading information, tips and tricks, a shotgun wad substitution chart, and frequently asked questions. As for recipes, most common cartridges are covered, as well as those less frequently encountered and some wildcats, too; however, know that not every chambering is there. For example, when I was searching for .450-400 Nitro Express 3” loads, the category didn’t exist. To be fair, there is little published loading data for it. Still, if you visit the website, I’m sure that you’ll find it to be user-friendly and quite helpful for your latest handloading projects. Do you get most of your handloading data from a published manual or online?
