BBTI - 44 Mag
Their nitty-gritty results for S&W 629 barrel length, velocity in feet/sec. for Federal 240 grain Hydra-Shok.
1296 fps for 6.5" barrel 629.
1227 fps for 4.875" 629.
1094 fps for 4" 629 Mountain Packer.
1120 fps for 3". 629 Mountain Packer with ported barrel.
You asked about energy. Kinetic Energy = Mass x Velocity Squared (must use a conversion factor). "The result is left to the student".
So, energy percentage differences will be greater due to the "squared" factor.
A VERY good energy difference approximation can be done just by looking at the percentage difference in velocity squared if the bullet mass (weight) stays the same, like in this case.
For the four cases shown above, I will call the 1296 fps for the 6.5" barrel "the baseline".
0 % difference for the 6.5" baseline.
-10 % diff. for 4.875".
-29 % diff. for 4" 629 Mountain Packer.
-25 % diff. for 3". 629 Mountain Packer ported.
The result for the 3" ported seems "counter-intuitative" to physics. I have no idea why. But, actual tests.
And, my opinion.
Unless you are in Grizzly, Kodiak, or Polar country, I wouldn't worry about carrying a 3 or 4" barrel gun using a "premium" .44 Mag hunting load. YMMV.
Also, other threads here discuss using a semi-auto 10mm hunting load (Glock 20) for extra rounds. Also a good choice IMHO.
No problem with the lighter gun. But, at purchase you must present a notarized letter from your mental health professional.
"xxxxx is certified by me to be suffering from a severe case of a masochistic personality disorder".