I havent been trying to develop loads for my 338-06 just loaded some up to fire since I also just finished my 338-06 project and wanted to fire lead down range. I had an 06 barrel and had JES open the barrel up to the 338 dia. I was using hornady 225 with IMR 4895 and had 3-3 shot groups less than 1 inch like I said havent worked on load development yet but very happy with my results.