gdolby ...
I shoot a .243 a lot and have primarily been using Varget until I decided to give H-380 a try. I am very pleased with some of my test groups. You mentioned the 55gr BT and 85 partitions. My rifle just doesn't seem to care for any bullet less than Sierra's 60gr HP. From there, I have tried 65gr V-Max, 70gr Nosler BT, and 80gr Nosler BT. All of my groups with the V-Max, 70gr Noslers, and the 80gr Noslers have shrunk with H-380. I do not judge a load by a single 3 or 5 shot group but several groups over a period of several weeks. I figure that temperature and other conditions will change and I am looking for a load that will perform in most conditions.
Here are some of my H-380 results at 100yds:
80gr Nosler ... 38.5gr ... 2.65 oal ... 3041fps ... less than .500" ... 5 shots
70gr Nosler ... 40gr ... 2.65 oal ... 3160fps ... less than .500" ... 3 shots
65gr V-Max ... 44gr ... 2.65" oal ... 3568fps ... less than .500" ... 5 shots
The best of these was the 65gr V-Max which also grouped under .600" ( 3 shot group) at 200 yds. The 80gr Nosler load is a minimum load and I have not tried any other load with that bullet.
I do not own a chronograph and the velocities are manual numbers. I was pretty satisfied with Varget loads that I was getting but kind of excited now about H-380 loads.