I ran a number of (non scientificly rigerous) 44 magnum bullet velocity tests over the years.
There are a number of incinsistencies here, that reduce the value of the tests, and I only wrote down some of them, while others were entertainment at the time and left to memory.
There are Good barrel length versus velocity tests, and some I know about were from Phil Sharpe (old writings, and reprinted maybe 10 years ago in Handloader) where he took a 30-06 service rifle and cut it back inch by inch to I think 12", some done by Art Alphin and published in the A Square manual "Any Shot you want", and soem good stuff at
http://ballisticsbytheinch.com/.
Much of what I found was, in revolvers, barrel length doesn't matter too much within practical barrel length changes.
A friend and I ran some impromptu tests w/ 310 LEE pushed by 22.5 or 23 W296, and I remember my 7.5" Ruger SBH running right about same (maybe 20-50 fps of difference one way or the other) of one of his 8 3/8 S&W 29/629 pistols at 1200 or there about, and his 4" S&W doing ~ 1100 fps. 100 fps of difference can be found gun to gun w/ same barrel length.
For some of the recorded "test data" I have below, remember that the cylinder gap on a revolver is a pressure bleed. A closed breach like a T-C has will add velocity due to trapping the pressure 100% in barrel rather than bleeding off (think of the cylinder gap like a really poorly designed waste gate on a turbo engine...).
Note the 30-06 test. I ran a Lot of rounds through my 30-06 Encore before it went away, and I have to say that I demonstrated to myself that fast powders are Not required when a barrel is cut, and loss w/ this type of expansion ratio is ~ 1% per inch.
305gr LBT LFN GC Buffalo Bore "Heavy 44 mag":
1380 fps, 7.5" Ruger SBH
305gr LBT LFN GC Buffalo Bore "Heavy 44 mag":
1590 fps, 14" T-C
305gr LBT LFN GC Buffalo Bore "Heavy 44 mag":
1660 fps, 20" Marlin
280 gr Mountain, 44 Remington Magnum, My design, BHN 27, W296 25 gr, WLP:
1440 fps in Ruger SBH revolver,
1600 fps Stock 12" TC
260gr LBT WFN GC, 44 Remington Magnum, 20.5 gr WC820:
Stock 12" T-C @ 1500 fps
Stock 14" T-C @ 1500 fps
7.5" Ruger SBH @ 1250 fps
240 gr West Coast plated FMJ, Remington Magnum, 20.5 gr WC820:
7.5" Ruger SBH @ 1220 fps
Stock 14" T-C @ 1440 fps
30-06, 220 gr Nosler Partition, 54 gr IMR4831, Rem 91/2
2260 fps, 15" T-C Encore
2448 fps, 23" sporterized 03 Springfield