Need some sugestions

[Martini2]

Hello Sir Kurt. Please pardon that this reply on caliber selection has arrived post thread changing to most recent topic.
It takes a long time for those electrons to float all the way East here to Ohio The latest discussion on thread has drifted to "fuel for thoughts" while I was researching my reply. Possibly dipping a cup in recent conversations helps thinking up new things too FWIW in main discussion of Brass with smaller rims to fit your project rifle a candidate comes to mind. In publication "Down Range Data" William T. Falin extols on virtues of his design of a 40-444 or 40 Falin. It is based of course on 444 Marlin brass with 0.514" rim dia. He runs the full length brass into die that is tapered to 0.750" from case mouth were it turns into straight neck. Falin's game and 100 + page booklet covers long range BPCR shooting. His book particularly involves Billy Dixon range and ballistics for 1540 yard shooting. Best regards all RobertB