.010-.015" off the lands is a good place to start.

Never got the best accuracy out of Speer BT bullets..........for almost any new rifle, for load testing & accuracy trials, I almost always start with Nosler BT's.

They are very dependable, accuracy wise, & cheap enough to consume a few or more, for testing.

Rarely doesn't work...........assuming all else is good.

4350 (either flavor) is a very reliable starting powder for an '06, but Varget is also. So likely you are Ok with either of those until you can ID something else.

MM