I was at the range a few days ago to break in a brand new Kimber Montana in 280 AI. We did no formal barrel break in but fired 24 rounds in 8 different loads of 3 each. It pretty much shot everything into 1 inch 3-shot groups at 100 yards. This was using the 145 grain Barnes LRX with H4831SC. Since there wasn't much difference between the groups we decided to go with the max load we tested of 60.5 grains. Primers looked good, no pressure signs so there is probably a bit more room on the upside. If you check the Nosler handbook (it is available on line) you will notice that max loads of IMR7828 are compressed so the SSC version is the way to go. It looks like you would get up to 100 fps more velocity with IMR7828SSC but temperature stability may not be as good as the H4831SC. Try them both and see what happens (forget the Varget).