In the early 80's I installed a Shilen 1.125 dia bull barrel on my 25-2 revolver and blued the barrel only at my place of employeement. We had a heat treat and bluing facility and we used Heat Bath Corp. products and the bluing tank was kept at 280-290 degrees. The barrel was buffed to a mirror finish and ran through the bath when I installed it on the frame you could not tell it from the original bluing on the 25-2. I think it is in the polishing of the part. The tool holders that were blued in the bath all had a milled finish and all came out black. Jeff