Total amount of transferable heat on the projectile

There is a third factor, not as important as the previous two, that limits the amount of heat that can be transferred to the target by a projectile, namely the total heat content of the projectile. We give a rough estimate of it in this paragraph. Assuming for simplicity that the outer layer of the lead bullet had a temperature of $220\tccentigrade$⁴¹, with a mass which is $25\%$⁴² of its total mass, 3.88 g, while the rest of the bullet was assumed to be at room temperature, about $30\tccentigrade$. The heat capacity of lead is $129\ {\rm J}/{\rm kg}\tccentigrade$. Combining the above data, the total amount of thermal energy carried by the lead bullet transferable to the skin at normal body temperature, is approximately 21 joules, or about 5 calories⁴³according to the law of conservation of energy.⁴⁴

What can be achieved with 5 calories of heat?⁴⁵Well, it can raise the temperature of 1 teaspoon of water by $1\tccentigrade$. Such a small amount of heat, delivered by an inefficient cauterization instrument, the bullet, surely cannot cause burn injury, not to mention burn marks.