I use RL15 for my Whelen, and I load to the old Speer and Lee manuals for it. The pre-2018 or so Lee and Speer manuals list a max of 59.5 grains of RL15 for the Speer 250 grain HotCor. At this charge, I get about 2670fps from my Remington 700 with a 24" barrel, with some primer flattening...