I see shooters making there own special purpose loading blocks. For sure the standard block are pretty cheap & amply available. But the DIY'ers may want a tall, thin, thick spread out, large/small number of holes, etc. It seems like you must have a CNC machine to make one. Also, I guess you need a flat-bottom mill for the work.
Can you get by with a plain drill press & fostner bit & old drill bit ground flat? Anybody tried it?