I recently purchased a used Mountain Molds 300 gr mould from an auction site for my S&W 629. It was more weight than I wanted, but the price was irresistable. Anyway, when I received it, I discovered (happily) that it drops a 280 gr bullet with 50/50 WW/lino. I just did my research, and decided to start with an unlikely load of 10.0 gr of Unique. This should give me approximately 950-1000 fps, which is my goal. I want to keep the velocity down a bit because my 629 is an older one, and doesn't have the updated lock work. I've seen 10.0 gr of Unique listed as a safe load for 300 gr cast bullets, and its right in the upper middle range for a 275 gr cast, according to Lymans data. If it will help, Lyman used to offer a 275 gr mould, (429640), and there is loading data still available for it. I'm also going to load a batch with 2400, to see which I like best. I have not fired my Unique load yet, but should be able to in the next few days. I'll let you know how it turns out.