I have a Marlin Guide Gun in .45-70 for BIG bear country.
Relatively short barrel, but not down to 16 inches.
As a general rule, anytime you LENGTHEN a handgun caliber, you gain velocity, which can increase energy & terminal ballistics. Anytime you SHORTEN a rifle caliber, you do the opposite, to at least some degree.
Bullet construction also becomes a factor.
A rifle bullet designed to expand at a certain velocity range may not when reduced too far.
A handgun bullet designed to expand at a certain velocity range may violently fragment when driven beyond that range.
Lead solids tend to perform more consistently through a wider range of velocities & be less affected by increases or decreases.
Penetration may be reduced in dropping down, but the bullet typically won't be demolished on impact like a jacketed type driven too fast can be (which reduces penetration when that happens).
It's a balance.
I have a mid-weight Shiloh Sharps with a 26-inch barrel & a Lyman Model 1878 with a 30-inch barrel, both in .45-70.
I could feel as comfortable with either using the right bullet in grizzly country as I could with any single-shot, but neither is anything I'd want to carry far or long in hand.
I'd want a repeater, and the Guide Gun does it for me there. Not 3exactly light, but lighter. No 1000-yard gun, but it doesn't need to do much over 50 yards, it's a dedicated defensive package. Recoil with the Garrett heavyweights is not much fun, but neither is getting mauled by claws.
Elsewhere, the 16-inch .357 & .44 are both trim & relatively powerful, enough to make a great compromise out to 100 yards between totability & power for anything black-bear-sized or smaller, and that covers most areas I spend dirt time in.
Lead solids, or a jacketed softpoint.
Either of those can be paired with a good handgun in the same caliber.
Shorties are neat & peachy keen to carry & look at, but I think a 16-inch .38-55 would just lose too much in one.
Depends on what you'd want it to do.
A 16-inch .38-55 would not be MY choice as a bear gun.
The .357 wouldn't be first choice, either; the .44 Mag with the right bullet could handle blackies.
Denis