I vaguely remember something about being able to go one way but not the other. Maybe you can make a rifle from a pistol action, e.g., XP-100. Anyway, that doesn't matter much with me because I would buy a complete pistol from a smith.
I am thinking I would want as long and heavy a barrel as possible, with some small and efficient cartridge. I am thinking it would be a bolt gun with a custom barrel. (Is a factory XP-100 worth considering?)
Anyone know a good source? All I know of is the XP-100, but I see other guns listed that I am not familar with in Sierra's manual: Wichita, MOA, for example.