A .504 (have them copy the White Barrel) caliber in a 28" stainless steel barrel with a 1-24 twist. Also, with a high quality lock. Synthetic stock also. Make this into a good hunting rifle. Also make sure the trigger is a single trigger with a very crisp break. A Timney might be nice as long as it breaks real clean and not sloppy. Also make sure the rifle can be removed from the stock, either with locking lugs or a tang, but it can be removed for easy cleaning. A removable breech plug would be nice too, like the PA Pellet or the RMC that was around. This would make the shooter positive that the barrel was spotless and make the rifle easier to clean.

This would make a easy to maintain, easy to carry, weather resistant, large caliber legal in all states for all large game, conical shooting monster. Also with this twist as we know, it could also shoot sabots for those that hate conical bullets.