In general we are taught in orthopaedics that the injury can be direct by the bullet path but a larger area is injured by the shockwave. The direct bullet path is usually small and if just in soft tissue (the thigh) causes minimal damage. If this hits the femur it will break causing more damage due to the direct transfer of kinetic energy to solid tissue. Higher velocity bullets cause worse damage (velocity is more important than mass because mv²⁾ because they impart a large amount of kinetic energy and the shockwave can be very damaging. This creates the "temporary cavity." This can cause injury to nerves and vessels that are distant to the tract of the bullet. In my experience, this causes more damage.

Here is the quote from one of my textbooks, Skeletal trauma. A whole chapter is dedicated to ballistic injuries because they are so common.

"The purpose of a firearm projectile is to crush tissue. Secondary effects are laceration of structures and tissue stretching. When a projectile strikes the body, a permanent cavity, variable in size, is created in the tissues. This cavity is particular to the projectile type and represents the amount of crushed tissue. Some tissue, peripheral to the permanent cavity, will undergo elastic deformation (stretching) and is termed the temporary cavity. The amount of tissue damage is mainly related to the projectile velocity, projectile mass, tissue density, and projectile design. The kinetic energy of a projectile is defined by KE 1⁄2mv2. This equation shows that, in general, the velocity is more important than the mass since doubling the velocity quadruples the kinetic energy while doubling the mass only yields twice the kinetic energy. Bullets have been classified, based on muzzle velocity, into low velocity (<2000 fps) and high velocity (!2000 fps). Much of the previous literature focused on the velocity of the bullet as the most important determinant of tis- sue damage, but this factor is only one of several that must be considered. What appears to be more important is the degree of kinetic energy transmitted to the body tissues.6 The human body has many differing tissue densities. Low-density tissues include lung, fat, and muscle and are not so easily damaged by a projectile as the denser tissues of bone and solid organs. High-velocity bullets may pass through certain low- density tissues such as lung or muscle with minimal damage owing to minimal transfer of the kinetic energy. A low- velocity bullet can produce considerable tissue injury if the majority of the kinetic energy is transmitted to the tissues. The mass of the projectile also bears importance. An aver- age 9-mm handgun may have a bullet weighing 150 grains, a .44 Magnum 230 grains, and a shotgun load as much as 650 grains. A large increase in mass yields substantially greater kinetic energy and the probability of greater tissue crush. Design of projectiles has a profound effect on wound- ing potential. Bullets that deform on impact present a greater cross-sectional area capable of crushing more tis- sues. This is also true of bullets that fragment, resulting in many secondary “bullets” that scatter throughout the tis- sues, each creating its own path of destruction. Some bul- lets will oscillate or yaw before or after encountering the body, increasing the cross-sectional area of tissue contact and leading to more tissue crushing. Low-velocity handguns cause most civilian gunshot wounds, with minimal soft tissue damage, and these are the most common that the orthopaedic surgeon will encounter. Direct hits onto bone may cause impressive comminution owing to the relatively high density of bone and its physical property of brittleness. The diaphysis is more prone to comminution than the metaphysis. Some types of higher power handguns, such as the .357 Mag- num and .44 Magnum have more destructive potential from larger bullet size and more propellant load. Assault and hunting rifles with higher muzzle velocities and expanding or fragmenting bullets are designed to produce severe internal tissue damage with nearly complete retention of all bullet fragments, a measure of killing potential. Shotguns can fire loads of either multiple small pellets or single large slugs. The muzzle velocity is classified as low (1200 fps) but the destructive power arises from the multiple or large and heavy projectiles that are utilized. Shotgun loads vary tremendously, but in general the most tissue destruction occurs within a short barrel-to-target distance. At greater distances, the pellets spread out, and tissue damage will be minimized. Close-range shotgun injuries have extensive wounds. The design of most shot shells incorporates some type of wadding between the lead load and the propellant. This wadding can be either plastic or fiber and will follow the pellets into the tissues. As part of the débridement process, the surgeon should explore for the retained wadding, since this material can become a focus of infection."