Barry,
I think you will really enjoy owning a 257 Weatherby. If I read this thread correctly you don't handload. I suggest you start with HSM's 257 Weatherby ammo using the 115 Berger VLD.
Trophy Gold
It is a high BC bullet with excellent killing abilities. I think your approach to making one is admirable. It won't cost you much money yet you will have the chambering you want. If you want more performance handload. Your choice.
I have written this so many times here that some of you are probably sick of hearing it. We built 5 257 weatherby chambered semi customs a while back. We ordered a PTG reamer with a slightly shorter throat and a 1.5 degree throat angle. Our jumps ranged from .070" to .100.
All used the 3 groove Lilja SS barrels. Two were #5 profile 28" long. The rest were #3 profile SS two were 26" and one was made as a lightweight with a 24" barrel. All used RL-25 with the 115 Berger VLD.
I lost count and have to get back to Tim and Allen but to date combined we have killed 20 deer, 6 elk, one antelope and two javelina. The long barrels were getting 3675 fps with the moly coated 115s. 26" barrels got 3600 (uncoated) and the 24" got 3550 fps (moly coated). By the way that 24" gun weighs just under 7 lbs and has taken all the elk.
Recently my 28" barrel got rough and at round count 550 or so, IIRC, it began to destroy the thin jackets on the VLD. I switched to moly coated 110 accubond and also moved to RL-33. Getting a stunning 3735 fps with this old barrel. Recently shot it and had a friend shoot it, the two shots were in one hole at 100 yds.
When I rebarrel this rifle I won't use it as a test bed for a wide variety of bullets and powders. I used it to shoot jackrabbits and rock rats too. I shot the heck out of it while my three friends just stuck with the 115s. Their rifles will last their lifetimes as they only shoot it to kill big game.