I did a search and came up with a wealth of info. I'll start with RL22. Looks like 100 gr bullets are the most popular for most of the 257 users. I have RL22,25, and IMR7828 sitting around so one of those will probably do just fine. I did see where one guy claimed some great results using ramshot magnum. That peaks my interest as its a ball powder and purportedly easier on throats.