Originally, it was about 1450fps and that is easily attainable with standard pressure handloads. For some reason, people think 1200fps is a "magnum" load. In reality it's just a .44Spl Keith load in magnum brass, which is going to be even lower than the 26,000psi Keith load. The oversized cylinder allows me to push to +50,000psi and the length allows me to use the lower crimp groove in bullets so-equipped. So I basically load them to 100% density and get a 330gr LFN to original 240gr velocities. Which you can also do in the RH and SRH.
The folks who say it exceeds are just reading the nearly 40yr old Linebaugh article, quoting it as gospel and never bothering to test for themselves. The truth is it will nip at its heels but never quite matches its velocity with same weight bullets. The .44 is usually 50-100fps faster. The .45 is a wee bit bigger (meplat is usually only .005-.010" larger) and the .44 is a better penetrator. Net result is a wash.