Having used the RCBS and many other designs, I have to tell you that its design is among the worst because of friction between cases and the V blocks. If you want to measure the runout of loaded rounds, and correct the runout (not recommending just saying if) the H&H cannot be beat. For measuring the runout of cases, the bearing balls that Sinclair uses are the lowest friction of any that I have tried. On the Hornady tool, it has a design flaw in that the body of a fired, and sized case, above the solid head is usually not symmetrical with the rim of the case. IMO, custom one piece dies that have the neck ID correct give the most consistently low sized case runout. The other way to approach this, that I have done several times successfully, is to design a tight neck chamber reamer so that the neck tension is correct without an expander ball, and loaded neck clearance is correct with necks turned to design thickness. With this setup you can have say .003 neck tension with no expander, and .002 with, and with the expander doing so little work, concentricity is not reduced. The amount that cases are reduced in body diameter in sizing also gets into this, and believe it or not, a friend found that his lube pad was distributing lube unevenly around the case and causing a concentricity problem that went away when he applied the lube with his fingers. It seems that people get some sort of emotional satisfaction from tightening things snugly, metal to metal, but I have found that Lee lock rings, that have a built in O ring, can improve results. Just remember to just snub them enough so that the die is secure from rotation in use, and not so much that the metal of the lock ring touches the press. Carbide bushings are more true than steel or coated steel. so if you use bushings, and they are available in your size, you might consider that. Recently I tried out a new S type Redding die, dropped in a new bushing and sized a case, and was severely disappointed with the runout. It turns out that the problem was the preservative oil was in the bottom of the bushing cavity was the problem. Once I cleaned that out, the die worked as it should. Even with "experienced" dies, this is an area that needs to be cleaned from time to time. If you have to get by with a cheap one piece die, and want to get the best results, after you hit the top of the press stroke, lower the ram enough to be able to turn the case, and turn it 90 degrees and run it back to the top. Do this three times so that you have sized the case a total of four times, and then instead of using the expander ball to open up the neck, use a expander mandrel and die, with the inside of the necks lubed. This will take longer, and involve extra work, but the results will be a lot better than using the die conventionally. The latest experiment that a friend did at my suggestion (He has a lathe, I don't.) is to check the faces of lock rings for runout. Forster and Hornady were the best, the ones that are solid and do not have a piece of lead shot under the tip of the screw were the worst. He trued up his lock rings, and a bunch of mine. The ones that were the worst type were not done, because they would not set consistently to the same angle.
