Here's my apples to kiwi fruit comparison from my Speer reloading manual.
All are max velocities found for that particular bullet weight. Not the barrel lengths are an uncontroled variable.
.357 Mag 158 grain 6" handgun 1,034
.44 Mag 240 grain 7.5" handgun 1,450
.357 Mag 158 grain 18" rifle 1,738 +68% over handgun vel.
.44 Mag 240 grain 20" rifle 1,738 +23% over handgun vel.
Note that the .357 mag in a pistol using 125 grainers is doing 1400-1500 fps.
Okey-doke. I couldn't find any data for a .44 Special out of a rifle, but I have it for a puny 3" handgun.
240 grainer coming out at 863 fps.
So, if we were to give just a 23% bump in velocity for th e.44 Special out of a rifle, that would give it 1,450 fps which would put it at the same energy of a .44 Mag out of a handgun.
Would that be something worthwhile?
Rick