While I don't have direct experience with this particular combination, I do have a bit of experience with Accubond LR bullets, Loading for .300 Win mags and Ruger No1s. I load for 4 of them.
I would first start with using a slow powder like IMR7828, Retumbo or H1000. In this case I would use IMR7828.
I use IMR 7828 and a 180g Berger Classic Hunter in the .300Win Mag I load for.
If you could get a quality magnum primer I would go with Federal GM215M Match primers if you can find them. I use them in my 7mm STW and they helped a lot in shrinking my group size. (CCI250s if you can't)
As far as the COAL, That really depends on the throat of the rifle. Every Ruger No1 is different. The two 7mm Remington Mags I load for are different vintages and have different throat lengths.
The wonderful thing about the Ruger No1 is that being a single shot, you can seat way out if necessary to achieve your greatest accuracy with out worrying about a magazine length. That being said you still need the bullet to be held in the neck. The neck of a .300 Win Mag is only .264" from shoulder to mouth. So there should be plenty of bullet to seat in the neck.
Using a fired case. Size the neck slightly and then seat the bullet in increments, checking the "dummy" by putting in the chamber. Continue to do this until the bullet gets seated by closing the breach. Eject the shell then use it to "set" the die, then set it 1/2-3/4 of a turn more so the bullet doesn't touch the rifling.
This is where I start all of my COALs for Ruger No1s and best accuracy is usually achieved using this method.
Start 5-7% below max book with what ever powder you choose and work up.
Hope this Helps,
Dan
