Jerry;
Before you invest money in a new barrel, you might want to do a good cleaning of your barrel for any copper deposits. I have seen several rifles that had their groups open up and it was due to excess built up of copper jacket material. Removing the copper will normally allow the rifle to return to the point of shooting good groups. If it turns out to not be a copper desposit problem, then you may have a throat erosion problem. If this, go ahead and replace the barrel. For the copper cleaning be sure to get a solvent that is made for removing copper, regular gun solvent will not do this. Do not stop cleaning until the wet patch stops coming out of the barrel with a bluish color on the patch. It may take several hours and numerous cleaning until you get a clean barrel.
RELH