The only test we actually did on a similar subject was for and velocity differences between rifled and smooth.
The "premise" from the 1860's book, stated that a smoothbore gun will deliver higher velocity per charge, than the same bore size gun with rifling.
Our tests showed virtually identical velocities with the same powder charges and ball.
A 20 bore smooth bored gun and .62 calibre rifle were used in the test. The rifled gun needed much thicker patching to use the smooth bored gun's ball,
of course, yet the velocity difference between them, was within variations of shot to shot velocity spreads - less than 20fps, certainly nothing meaningful.