All the above are good advice, in my opinion.
If your chronograph is too close to the muzzle, you can get faster velocities, as it may be reading the muzzle blast, but that is highly unlikely in this case, as such mis-readings are most always HIGHLY erratic.
If there is another 44 Mag gun around, you might try shooting both guns with the same ammunition over the same setup.
The "fast barrel" conjecture looks likely at this point.
p.s. for more information about barrel length and velocity, check out the site "ballistics by the inch"
started by a couple of guys with an intense curiosity and enough time on their hands to satisfy it, and a LOT of lead.