Use the data from Hogdon.com; good stuff. Remember that pressures come up very quickly with few or no warning signs, so make your steps up in 0.5 to 0.2 grain intervals. Use your chronograph readings as a guide: fire about five factory loads to establish a goal for your particular rifle and load up slowly until you match your goal. There's no point to pushing the envelope - all the short mags are already there at the limit. My first "pressure sign" was when the bolt locked up! No flat primer, no sticky extraction, no creeping pressure ring at the base.
H-1000 may be a good choice, it works wonderfully in my 243 WSSM, which is one of the most accurate off-the shelf rifles I've ever owned. Shoot slowly or you'll vaporize the throat out of that barrel in as little as 500 rounds.