There are a few smiths that do not want to use a M-700 action to build a 338 Laupa on,but there are more that will, a short list of those that do George Gardner,Shawn Carlock,Kirby Allem.Chriss Mathews...to name a few
I built my 338 Laupa on the M-700 Action,because it is easier to go to a detachable box mag.that will take a 3.9" OAL cartridge.No bolt stop issues
Here is a picture of mine
M-700 Action, ABS Carbon Wrapped barrel 30" long Rem Sendero stock and 5.5X22X50 NXS scope total package 11.6 pounds........
The action would have to be opened up ,you would be money ahead to start with a 375 H&H action as it is already opened up.... It would also need a longer magazine... All of this can be done,it just cost money.... To go to any 30-06 length mag cartridge will only require the bolt face to be opened to accomedate the larger rim of the bigger, not longer round