If you want to buy new brass, Sinclair Ineternational has it in stock now. Midsouth Shooters Supply and Graf and Son are both out of stock at the moment but say they should have it in by the end of December. Lots of gun shows have brass and powder dealers who offer .257 Remington Roberts brass. As it is supplied by both Winchester and Remington, you can take your choice but I would suggest not mixing the two, there is generally a slight difference in case capacities.