E27 seems to have missed the point of shortening the die Tinker - shaving a few though of the bottom of the die, for straight sided cases, that is, effectively reduces the diameter of the inside of the die at the base, which in turn sizes the case down a couple thou more. The die must then be polished around it's new base. Some guys grind a bit off a shell holder, but I find that unnessessarily weakens the shell holder. I prefer to grind some off the base. All brass is tapered - shortening the die reduces the inside diameter at it's new base. This 'system' doesn't work for bottlenecked cases where the shoulder will get pushed back (unless that's the reason for shortening) - it works splendidly for straight cases for reducing the base diameter of the case being sized. Some brass, like .348 Win. brass is so heavy in the base area, that a few thou. can be turned off the base in a lathe - others don't have that much material, and swaging or sizing is necessary.

FL and seater dies can also use used for bullet sizing - match the sizes and tapers you need and shove the lubed bullet up inside to a preset level, then push it back out - the result is a tapered, lubed bullet.