To the OP, just go buy a .257WM Vanguard for not much more than a conversion would cost..
I actually suggested that idea in my first post.
I have nothing against the .257, its a fine caliber. If you want it, by all means have one. This po' boy just cant justify the cost of ammo for it.
Blessed be the Lord my strength which teacheth my hands to war, and my fingers to fight -Psalm 144:1, KJV, a Psalm of David