338/300 win mag
how expensive would it be to turn a 300 winmag and neck it up to a 338
Necking up a 300 Win Mag to 338 would essentially give you a 338 Win Mag. This would require a 338 barrel as well. Not quite sure of what you are asking or if this answers your question.
But if you want to have a 300 rebarreled to 338 a rough estimate would be $200 for a reasonable barrel and anywhere from $150 to $300 for gunsmithing, depending on if you wanted the action squared in the process.
The .338/300 is a .300win case necked up to .338 diameter.
It is larger in terms of capacity than the .338 win because the .300win case is .102 longer.
I have a spare barrel in .338/300 if you have a Rem 700 magnum receiver. 24" BDL barrel. Basically this is a standard .338win chamber improved to the .300win case dimensions. I have a Clymer reamer.
The .338/300 is very flexible and can about equal the .338 ultra and .340 wby. It will shoot light loads with heavy bullets unlike the bigger magnums, without danger of detonation.
If you want more power and better Ballistic performance than any .30cal can provide, the .338/300 is worth trying.