Art, the 300 Jarrett needs a long action and for me at least, would require a scope intended for long actions with plenty of mounting latitude.
They seem to be getting in "shorter" supply. The 6x36 will work on a LA but the 6x42 doesn't come back enough for me.
I have the 6x42 on a number of long actions without issue... The idea of bringing a rifle that likely weighs as much as the Jarrett on a sheep hunt is foolish, though I have done it before and the potential grizzly hunt makes it understandable...