How do you guys go about working up loads for a cartridge when there is no reloading data? I have a 350 Griffen & Howe that I want to expand my reloading for it. The only data I have found is the 2 loads in Cartridges of the world. I have been using IMR 4350 with 250 grain Swift-A-Frame. I would like to try some other powders along with some 225 grain bullets but how do you decide a good starting point/powder? The 350 Griffen & Howe is a 375 H&H necked down to 35 caliber. Any thoughts or info would be greatly appreciated.