The Contender won't handle higher pressure cartridges like the 243, 30.06, or 308. You can use the 30-30, 35 Remington, 7-30 Waters in the Contender. SSK makes custom barrels for the Contender in many of the JDJ cartridges. Marlin 444 brass is used to form most of the JDJ's that are used in the Contender.