Okay, thanks for the pictures. In the post that I quoted, it seemed that you are talking about your brass. What you measurement is in your bottom picture is the chamber length. With an impression, like you have taken using the cartridge, chamber length is case length + step.
Keeping the 2.095 max length, that would change the neck to .513
This is another thing that threw me off track. This is not a "neck" measurement. It is the case neck plus the chamber's step.
Here is what I drew for your case. In this drawing, the greater length on the left normally reflects the cartridge overall length but I changed it to reflect chamber length so it matches your impression.
In order to make this as accurate as possible I would like to very the length of the neck. This is done as a simple linear length, not following the neck's angle. In other words it is two dimensional, just like it is represented in the drawing. What I do when I measure a case is mark it with a fine Sharpe or pencil. That way I'm not changing the exact reference if I come back to measure something else. I would also like to verify the case diameter that is circled.
This should be a good representation of you chamber. If you see any differences, please note them. The two measurements that I asked for above might change the angles for the shoulder/neck and step that are represented in this image.
No sense on pondering the bullet until these are finalized. What happens once these to drawings are correct is the software will generate a bullet that fits the chamber. This generated bullet needs a bit of editing as it is simply filling the throat with lead. This is were it is a bit weird, your chamber from your impression, doesn't have any leade. It simply goes from step to the bore/groove. This is also why I don't think a .311" will not work in this application. The step is going to size to .3085" (think of it as a sizing ring) immediately.
Are you getting that “no good deed goes unpunished” feeling yet?
No, not yet. This is a slow process. I should have just started a bit different. As long as you hang in, so will I.
