Big, my 280 is in a Sako 75 Hunter, but I think Tikka makes one also.
Actually the "recommended" powder for 140 and 160 gn Nosler bullets is Reloader 19 (they list it also as having the best velocity). For 150 gn bullets it is IMR4350.
OF course the problem with the Nosler data is that for some reason they use a 26" barrel for their testing. My barrel is a smidge short of 23".
Cam, can you tell me how many grains of Re-19 or Re-22 you are using?
Long