I believe just about any non-expanding bullet will "overpenetrate" if shot into a human of about average size, barring the extremely tiny calibers.
I have no idea what the muzzle velocity of a Dragoon is, but here are some peretration figures on .454", 140 grain round ball that a calculator I programmed spit out, assuming the balls don't deform:
250 mps, 43.4 cm gelatin/flesh, 4.6 cm brick, 13.8 cm wood
300 mps, 50.1 cm gelatin, 6.1 cm brick, 17.9 cm wood
350 mps, 55.7 cm gelatin, 7.6 cm brick, 22.0 cm wood
400 mps, 60.8 cm gelatin, 9.1 cm brick, 25.9 cm wood
450 mps, 65.3 cm gelatin, 10.6 cm brick, 29.6 cm wood
If the balls flatten out to 15 mm:
250 mps, 25.7 cm gelatin
300 mps, 29.6 cm gelatin
350 mps, 32.9 cm gelatin
400 mps, 35.9 cm gelatin
450 mps, 38.6 cm gelatin
These numbers should be taken with a few grains of salt, but I've found that they correlate
very closely with real-world data most of the time. For instance, in the real world, a 16" naval gun penetrates 36" of steel at point blank range (2,700 pounds at 2,500 fps); my calculator says 39". A 4.5mm steel bb at 590 fps is supposed to go 8.5cm into ballistic gelatin; my calculator says 8.56cm.
This link says 32 cm penetration on the FBI load, my calculator says 30.7 cm.
Pretty darn accurate, I'd say.
Also, keep in mind that while the average male torso is about 23 cm thick, skin on the entrance side is the equivalent of 5 cm of gelatin, and skin on the exit side is more like 10 cm. Bone is completely different, and can make bullets do crazy things.