That 177 would be my choice in that chambering and twist. I am working on a load for a buddy from california, but he has a factory remington barrel, so the 143 is what we are limited to.
I have not shot any yet, but I have a box of 285's for my .338 Norma Mag, and then the 7mm 143's are on order. From talking with steve and others here, just start at your longest OAL, eaither mag box or a little off the lands, .020" or so, whichever comes first, and start working up till you see pressure and you will usually find a good accurate load. I guess you usually don't need to adjust seating depth to find accuracy....and start with load data from a similar weight lead bullet, and you will generally end up a little higher charge with a little more speed than a similar lead bullet.
All just things I have read and spoke to steve about with the hammers, no first hand experience yet, so take that for what it's worth. Good luck, please let us know what you figure out.