The .375 JDJ is a proprietary cartridge, and only SSK sells the dies. However, you can get the .375-444 dies from RCBS's Custom Shop and they are the same thing....but they aren't cheap either. Look on eBay, I see them there on occasion.
Making .375 JDJ cases is easy, just a single pass of new .444 brass in the .375 FL die.
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