All I know is that an adequate sized entry hole and a good sized exit wound coupled with internal damage through the vitals forward of the diaphragm usually lets the air out of them pretty quickly. I am constantly amazed at tales of double lung and/or heart shot ungulates running hundreds and hundreds of yards. I have to believe most were due to sorry shooting, but that's just me.
A quarter horse can cover 440 yards in the low 20s, carrying a rider and live through it. A bored person can hold their breath longer than that. Bleeding to death takes time.
A fatally hit animal can cover a lot of ground in the time it takes to say "I think you hit him pretty good, I think it'll be OK".
