I shoot cast 200gr SWC and 325gr GC RNFP. Both using wheel weights. For the lighter bullet, titegroups works very well lit by Win LP primers in Starline brass.
I use H110 for the 325gr monster. You can find load data on the Hodgdon site. There is new data for modern 45LC rifles and HG's now.
I also found lots of great info and data in Handloader/Rifle magasine. Actually, where my project started.
Both loads shoot extremely well and do give a sizeable increase in velocity over a HG. The 200gr goes 1100 to 1200fps depending on how I load them. The heavy goes 1550 to 1600fps and will cut one big hole at 40yds using open sights.
As to whether Win brass is stronger or weaker, no feedback as I have started with Starline and haven't used up the brass yet. I do have a bunch of Win used stuff that will continue being used for reduced loads. I doubt any brand will wear out at reduced cast loads.
At my higher pressures, the Starline brass does develop a slight bulge around the case head. I thought the brass would certainly separate but after several reloads using my Lee dies, it is still going. I guess the brass is quite durable. Very impressed so far.
You can find a Lee 300gr GC mold but no longer the 315/325gr. What a hoot these bullets are. They just hammer and explode things at short and long distances. I water quench them and they hold together amazingly well. Haven't been able to stop one yet using water filled jugs and phone books and lumber.
This summer I hope to do a side by side with a 12ga slug and see which prevails. My bet goes to the 45LC and my trapper.
Jerry