There must be a couple dozen ".300 IMPs" Which do you have? Once instance, .300 Weatherby is an "imp" of the .300 H&H Magnum. Mr. Ackley's books list dozens. Mashburn. Ackley. (Full length H&H brass.) And the shorties for the Springfield, .308 Norma... etc. If nothing else, cast the chamber in cerrosafe or sulphur and measure... Then you can ask a questin that can be answered. HAPPY HOLIDAYS. Luck.
