YEARS ago, I decided that using a ream die before turning might have some advantage, because the inside of the neck would be cut so that it would be better aligned with the body of the case, and then when the neck was finished by outside turning, the neck would be better aligned with the case body. Cases are formed with reference to their outside dimensions with the result that any inconsistencies in their necks' thicknesses displace the CL of neck IDs away from the CL of the outside of the case. Normal turning indexes off of the inside of the neck, and if that is off center then the turned neck will be as well. My thought was that you cannot straighten something that is springy by only bending it to the point were you want it to be, you have to go past that point, which is impossible within the confines of a barrel's chamber.
RCBS supplied the ream die, which ended up having to be replaced because the machine that they used to size the inside of the die's neck did not have a way to hold the ID of the die in alignment while the operation was done. (The neck was honed with the operator holding the die in his hand.) The result was that cases came out of the die noticeably less straight than they went in. Then there was the matter of the finish that the reamer left on the inside of the necks. It was not smooth, markedly increasing the force required to seat bullets. Fortunately this went away after a couple of firings. The final nail in the coffin was that I could see no advantage by examining targets. The rifle was a tight neck .222 with Hart barrel. It could be reasonably argued that the rifle, and or my skill level were such that any slight improvement would have been obscured by larger issues. In any case, I decided that this was a solution for a nonexistent problem. The cases that I made conventionally, expanding and turning, measured and worked just fine. On the other hand, if you want to pursue this, knock yourself out.
