Physical disruption is a function of bullet KE being turned into work in the body. That conversion depends on placement (Muscle, organ, bone hits), bullet shape & design, deformation, fragmentation (if any), and available potential energy (KE). The more efficient bullets do a better job of turning these facors into perminant wound cavities.
Sometimes, as documented by Fackler, hydrostatic shock does play a part, such as when a high-vel bullet strikes a relatively solid organ, such as the liver. Then, the hydrostatic shock may produce temporary wound cavities of sufficient volume as to exceed the elastic strength of the organ tissue, resulting in greater than expected tissue disruption (tears). The issue is tremendously clouded by the disparity of data, research, individual reaction to a wound, the vast range of bullets types, callibers, energies, and the large number of places & angles a bullet might strike the victim.
Fackler, Hatcher, and Marshall all agree on this one point: Low energy bullets don’t kill reliably. The big issues revolve around whether it’s medium mass/High velocity, large mass/low velocity, or low mass/very high velocity thats most effective in converting a bullet’s KE into work.
Simply put, we’ve only a small glimpse into how bullets kill, while having a great deal of practical knowlege in creating bullets that kill quite reliably. Call it the down-side of empirical research.
To bring this back to the OP, the Minie Ball moves relatively slowly (as compared to modern bullets), and expands well, thus, it wastes relatively little energy on creating large temporary wound cavities, while putting most of it’s energy into creating large perminant wound cavities. The Minie Ball, should it strike bone, frequently pulverises the bone, creating many, many fragments, which the create additional tissue disruption as they fly about in the body. That’s one of the reasons a bone hit in a limb pretty much equaled an amputation, if you didn’t bleed out on the spot. Combine this with the animal fat-based lubricant, and grossly unsanitary coditions, and you’re talking about very serious killer.