Re: Sorting cases by weight
As explained to me by my old gunsmith, who won many . titles.
First, the theory. That most of the weight and the volume difference between one case and another is not in the headstamp, not in the sides or the necks. It is the thickness of the case head. To find out which case heads are thicker and heavier, and which are thinner and lighter, you have to measure them.
Take a number drill that just fits inside the neck, and cut it to length and put a point on one end, flat on the other. It must protrude a small amount so that you can use a dial caliper and measure the distance between the headstamp and the flat part of the drill bit. It doesn't matter which case you use but this will establish a baseline and for purposes of illustration, we can say that it measures 2.500".
Now, you need a long board with lines marked on it, in thousandths. The first case goes in the middle and every case after that will fall either longer or shorter, meaning the web thickness is either more or less than the first one measured. You can measure two hundred and line them up on your board.
When you finish, it no longer matters which was the base line case but you can see the pattern, from thick web to thin web. What I do is; first remove the low five and the high five, or ten? Then I divide the rest (usually) into three or four groups. I mark the groups with a carbide scratch awl on the headstamp. It doesn't matter where the mark is located but it could be on one side of (for instance) 243. So one group would be marked as such, "I243" and the next is marked "243I". If you want to mark more groups, scratch your mark on one side of WW, so it looks like "IWW" and the next group would be, "WWI". So, one mark, strategically placed, can forever identify 40 or 50 cases that have approximately the same volume. You can mix them in the tumbler and load them with identical amounts of powder, but shoot the cases together, and assume the volume and pressure will be about the same....so the theory goes?
This lasts indefinitely. The scratched mark is always visible, years later. What I usually do is mark 40 low and 40 high and 80 cases in the middle. I save to ten lowest and ten highest for testing purposes, whether I happen to be testing powder or bullets, rarely primers. I usually write on the wall which cases are lightest, heaviest, and so on. Works better for me than a piece of paper, I have scribbles all over my loading room walls; all I have to do is find the right one.
Now, is this better than simply measuring weight? I don't know, for sure, but I have been doing it this way for about twenty years and my loads are a lot better than average. This works best for precision bolt, if for a gas gun, I wouldn't bother.
You just have to be sure that your flash hole chamfering tool bottoms out the exact same, every time. It takes a new number drill for every cartridge, of course and you need access to a lathe, to put a point on one end. You can usually find a fractional, number or letter drill that will fit the neck perfectly so that there is no wobble.
So, this is intended to <span style="text-decoration: underline">measure</span> case volume, rather than weigh the cases to determine volume. As I said above, the given is that the case walls and necks are very close to the same, dimensionally, and the thickness of the case head is where <span style="text-decoration: underline">most</span> of the difference lies.
All I can say is, works for me. BB
