1-the bullet seating depth is dependent on a specific bullet shape, how a specific pistol chamber is cut and what length your mag needs. In all cases you should load up a dummy round to ensure you are not jamming the bullet into the rifling, it feeds from your mag ,is not being crimped on a undersize diameter portion of the bullet and is does not have excessive setback.
2-Bullet nose shape and general overall bullet shape can make a significant difference in powder charge. There is a considerable col difference between 115 jrn, Sierra's or Nosler's 115 jhp and Hdy 115 xtp. This leads to differences in bearing surfaces and available volume for powder. The nose shape of Winchesters 115 fmj lets it be seated out further than some others.
3-There are several loadbooks that list COL, but you still need to determine what works in your pistol.