Another solution to the tight chamber problem is to neck turn or neck ream your brass, with turning being the best option of the two, as it eliminates varying thickness of the case mouth, which guarantees optimum bullet centering IN THE CHAMBER.
I strongly recommend that you lap the barrel, or at least check it out for precision using LBT push through slugs, as poor barrels are certain destroyers of cast bullet performance. Lapping it with the LBT bore lap kit will solve that problem.
Since the Lee mold is casting large enough for this oversize barrel, it bullets from it should shoot accurately at moderate velocities, but the design probably won't be strong enough for full loads, even with the barrel lapped. If you can't get tack driving accuracy after the above treatment, order an LBT mold to fit the new dimensions, and LBT bullet lubricant if your not already using it, and you will get accuracy, at full power. If your on too tight a budgit to order our mold, at least get LBT lube, as it will do wonders toward wringing the maximum velocity from any bullet design, this with accuracy and freedom from leading.
