Re: light weight long range barrel for 243 wssm
Stick with a factory barrel that has its bore chrome plated especially if you are going to use factory bullets. If you reload you will have to reduce the velocity to under 3,600 fps to prevent burning out an after market barrel that is not chrome plated. Ask me how I know.
Personally I would sell your rifle and buy a new one in .243 Winchester which will get close to the .243 WSSM, but more accurate and your barrels will last much longer. You will also be able to find ammo in any sporting goods store and the price will be less than half of the WSSM.