I have an 8-3/8" 25-5 w/big throats, and a 6" 25-9 that measures a consistent .452" all six throats. Both have some thread choke, 25-5 has .0006" thread choke, 25-9 has .0004" thread choke.

Another advantage of my 25-9, and probably all 25-9's besides correct throats, is it has a longer, thicker, deeper cylinder stop, which has to help stave off wear and keep lock-up tight for a longer time using those big, heavy bullets.