If you stop and think about it there are so many variables in how bullets will react . Air density ,air temp. , the alloying of the jacket metal , the alloying of the bullet core , the design of the bullets tip and base , the amount of fluid in the animal , is it well fed does it have a full belly or is it skinny with little fat or water in it's tissues . I may shoot a coyote today that hasn't eaten in a while so my bullet just pass's through but latter in the week I shoot a coyote that has just eaten it's fill so now my bullet explodes and make a mess out of this one . The people that manufacture the bullets know far more about what they are designed to be used for then I will even think about knowing . You can look at some 224 bullets as an example the 52 , 53 , and 55 grain hollow point bullets made by sierra for example they are all hollow points but the hole in the tip isn't the same diameter or the same depth and is designed for differing uses . The ojive isn't the same shape either . The base isn't either the 52, and 53 have flat bases while the 55 has a boat tail these give the bullet differing flight dynamics as well the jacket metal isn't the same alloy in them either being designed to be used for different types of shooting . The 52 and 53 grain bullets are designed to hold together and be shot at paper targets while the 55 grain is designed to be used for hunting so the jacket is made of an alloy that is designed to open up as is the core metal . Some bullets have slight scoring on the tips also to help in the expansion and fragmenting of the jacket and core . We have some 224 , 55 grain bullets that have full metal jackets that are designed not to open up but to penetrate and tumble on impact with the human body for military use . Some that have spire points that are designed to open up and mushroom causing a large but not explosive wound channel . And they are designed for differing amounts of penetration Some are designed to only penetrate a small amount and nearly explode , while some are designed to penetrate several inch's mushroom and cause massive tissue damage to larger animals . Still others are designed not to open up and go through an animal not causing much more then just the wound channel . The manufacture of the bullets and people like Brian Litz or Alex Wheeler who study bullets far more then most of us ever will have any desire to can tell us way more about what bullets in what caliber will do the best for our applications . Yes we all use bullets that weren't designed to do what we ask of them and for the most part we get by just fine with them .