Re: Neck Turning and Brass Sprining
Let me guess...you measured your necks' thickness with your calipers, because that fourth place 0 or 5 has you convinced that it is a substitute for a micrometer? As CatShooter said, brass does not magically reappear. As to the diameter of fired necks, there is some spring back, but usually not .002, more like .001 or a little less. If you do not have a 1' micrometer that reads to .0001 it is time to get one. As far as measuring neck thickness is concerned, as has been suggested, you can measure the shank of a bullet, seat it, and measure the neck with the bullet in it, making sure that there was some neck tension in the first place. Custom flat base bullets generally have what is known as a pressure ring at their heels. Sierras do not, for anything else, I suggest that you check them. When measuring for chamber neck clearance it is the largest diameter of the loaded neck that you will want to use, which will be over the part of the bullet with the largest diameter, so if a bullet has a pressure ring, you will need to measure the part of the neck where it is seated. The ideal tool for measuring neck thickness is some kind of ball micrometer, or case neck micrometer, that reads to .0001. When you measure fired necks' ODs, it is easy to compress the neck, so it is best to use a drag through approach, setting the mic., dragging passing the neck through, and then trying another setting the same way until you get the feel that you are looking for. A friend of mine was puzzled as to the results that he was getting and would not be convinced as to how easily the fine pitch of the micrometer's thread would compress a thin case neck, but I could see that is what he was doing. It doesn't take much to oval a thin walled brass tube at its end.
