Did you confirm the action screw spacing? Is the barrel the factory barrel, with the warning stamnps on the right side of the barrel in front of the nut and the "Savage Model 110 .243..." on the left side of the barrel in front of the nut?

You will need a magnum bolt head (after confirming the long action screw spacing). The rifle looks like a stagger feed action. Your magazine box and follower will need to be changed out. I'm not sure if there is a 300 RUM magazine box, or if a modified 300WM will work. Hopefully someone else can chime in.