About every ten or fifteen years, somebody has an article in The American Rifleman about barrel length and velocity.
I have read of starting with a 30" barrel and cutting back one inch at a time, although most start with a 26" for most rifles. 26" is the standard for published factory-ammo velocities.
My recollection is some 70 ft/sec per inch of barrel for the '06, .270 and .243, for whatever my recollection is worth. I've never seen a loss-number less than 60 ft/sec; I vaguely recall something like a 7mm Mag losing 100 ft/sec, maybe more.
You're gonna have to start somewhere and work up, for your load. Note I merely said that you'll most likely get the best results with 4064; I'm talking velocity only. It's possible that some other equivalent-burn-rate powder might give better accuracy. Otherwise, it doesn't matter if the bullet is coated or not, nor its construction.
If you don't have a reloading manual, go to any gunstore, look in any book, and see what starting load is listed for the '06 and 180-grain bullets.
Best luck, Art