I'm hoping some of you fine folks may have some starting load data for me. I know internet isn't gospel, and all loads need to be worked up to, and safety is first priority. That being said, I am having a time finding load data using Cast Performance 260gr WFNGC 44 slugs. I have H110, and CCI 350 primers on hand, and have a super accurate load for 240xtp using those, and am hoping to get the same consistency with the 260gr cast. I'll be shooting them in my Ruger SBHH, if that matters. Haven't seriously loaded any cast before, and I am looking for a good starting point. Thanks in advance for any help.

Start with your xtp load data. Cast bullets usually operate at lower pressures than jacketed bullet do with same given load.

Lee's Modern Reloading second edition lists for a 250 gr cast 23.0 gr H110 for 1602 fps.
For a 270 gr jacketed they list 19.5 to 21.5 gr of H110 so somewhere between those two.
They do not say what primer they use, but with magnum primers I would back off maximum loads a grain to start with.

Boot, From the website "Loading Data" It shows 18-22 grains of H110. If you do not get the desired results you might email or call them.

Remember this, that H110 performs best at more than 75% case capacity for each given bullet. As for me and some others this powder has given tighter groups at the higher velocities, at near or max capacity.

If you want to back off some, then I suggest switching powders and going to 2400. This is a stellar powder for less than max with lighter bullets. I have used it and 4227 with 260 and 265 grain bullets. Here 18-20 grains works well.

For a mild load that same bullet could be loaded with W231 w/8.5 grains. Or 9.5 grains of Unique. Both are nice loads.

Didn't mean to make this so long, but you stated that you haven't seriously loaded cast before. I just wanted to give you options and help.

X2