The benchrest crowd often has custom dies cut from blanks to match their chambers. It's full-length sizing, but not to produce a round that will fit just any old SAAMI compliant chamber out there, the way a standard FL sizing die does. There is a lot of discussion of bumping shoulders back just 0.001" with the special dies, so apparently they don't move the brass much. It's a different game from conventional reloading. Someone had a world record group standing for a number of years who just used a Lee Loader for his ammunition, and that tool sizes only the neck.
For the AR, though, you can only run your single-loaded slow fire rounds without conventional or sometimes even small base die sizing. Even then, in order to avoid slamfires, it seems to me that Glen Zediker was advising a 0.002" shoulder setback. I'd have to double-check that, though.
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