Manson. I've worked with Ray, who works there, on a remar and he's an incredibly helpful guy. Never fails to respond to questions through email. I can't imagine better customer service than he's given me.
I haven't got a jgs reamer, but hear they are top notch also.
That’s a very difficult cartridge to work with, think carefully before you throw a lot of money at it, the very thick neck, and shoulder angle tends to give trouble