240 Wby with a 1/8. I see no advantage to a 6/06.
Having owned and used both a .240 and 6mm-06, I disagree. Brass for the 6mm-06 is considerably cheaper, since it can be easily made from .25-06 brass--and the 6mm-06 has around 10% more powder room, due to a larger-diameter body.
As far as the other questions here, a 1-8 twist will easily stabilize any 105-grain high-BC bullet. It can be a little marginal with 115s, depending on environmental conditions. Mine shoots 115 Berger VLDs great, but the lowest elevation I normally shoot in is around 4000 feet above sea level here in southwestern Montana. It will still stabilize 115s in a typical Texas winter, but they won't have as high a BC as they would with a 1-7 twist. But if you're not interested in 115s, a 1-8 works very well.
