Originally Posted by PPR
Just a thought, but maybe you could buy a clip made for a .300 win. Mag that would give you the length that you need.
Great thought, as I believe that all Tikka rifles are all built off of a long action. However the 300 win mag is smaller in diameter than the 300 wsm, so this presents an issue. Winchester states that it's wsm line of cartridges is not based off of any other case, so we need to choose a magazine that has the same, or slightly larger internal diameter.
Body diameter at the base of the 300 wsm is .555 and it barely tapers over the 1.464-inch run to the start of the 35-degree shoulder. That said, it is smaller than the 404 Jeffery, so that gives us a great starting point of any of the RUM chamberings. If Tikka made a RUM anything you want that mag.
Of course there is always the much easier and better route of replacing the factory bottom metal altogether and getting an upgrade.