The .30/30 started life as a Ballard target cartridge, .32/40 well remembered. Little remembered, .28/30... Blown out straight, .38/55. Todays shape/pressures; 7mm waters, .32 Special and .375 Winchester. Ladies rifle, smokeless was the .25/35. Improved it screamed. .22? .219 Zipper, father to the .219 Don Wasp. Today there is a 'smith who works with the thinking of Mr. Ackley and Mr. Donaldson, Mr. Brown/ eabco.com. He has some house cartridges, one is a 6mm on the .30/30 Imp style case. Cute little single shot rifle too. Enjoy.
As suggested, there are 'smiths making the .308 family WITH RIM on the .307 or necked down .444 Marlin cases. You order the rim cut on a .243 barrel and you have a rimmed .243 with cases from the above. You use standard dies and the rimmed case shell holder to reload. Might be a little warm for some of the single shots. Not cheap. But you have a cartridge of proven value... And you can fire --IF SAFE-- the rimless ammo, just bring a cleaning rod for "ejection..." luck.