I think if a bullet comes in contact with the top of the heart and lungs..... it's pretty much DEAD! But if it hits a back edge of one lung or only the liver, and/or strikes the shoulder and blows up you've got problems! Big animals can over come what might seem like a major hit, you only think it was a perfect shot? But was it really or did it only nick a lung?
Shot placement is vital in any situation whether using a arrow or a bullet. Since when did shooting Big Game turn Hollywood? You know.... the bad guy gets shot and flies back from the shot to the ground like he was hit from a Mac Truck. I've shot Bobcat at four feet to only plink their eye on the shot through the chest with a 40 S&W! It does take a moment for the creature to die! Had I shot that animal in the head with my 22 LR pistol it would have more then likely fallen over dead from the shot.
I've shot Deer and Bear right behind the ear with a head shot, and YES they fall over dead on the spot. I've even dropped a charging Cape Buffalo with a 220 gr. Woodleigh Sold from my 30-06 with a head shot. But any shot to the lungs and heart they will run off and within a few minutes expire from blood loss to the brain and heart, and the lungs fill with fluid and then it dies! The bullet did its job, and whether it was a Nolser, Sierra, Speer or even a green box of Core Locks.
An Elk is a tough animal, and so is a Bison or a Cape Buffalo. Have you ever seen how long it takes for a 2,000 pound animal to expire to a shot? They don't just fall over unless shot to the head, but if a well placed bullet finds its mark within five minutes the animal will expire cleanly!
Case-in-point. Last night I had two mouse traps go off. One mouse got a direct hit from that trap! It took a direct hit to the neck and chest! Do you think it died instantly? No, it managed to pull itself and that trap a distance of over 14", and then die! The other mouse had only his leg caught, but broken very badly! He pull that trap from the back of the garage around the the front corner of the garage 24' until I finely found him hours later. I walked him outside and removed him from his leg hold. Now that mouse stood there for a moment breathing heavy but not completely in shock. He then started to scratch himself clean and run off to where he lives, with a badly broken leg! Let me tell you, if one of us had that bad of a wound, a broken leg turned backwards! We wouldn't run off like it was nothing! My point being is animals whether big or small can endure great trauma and run off great distances and even greater distances when pushed by hunters unaware they where not wounded fatally!
I've shot game with just about every known bullet maker out there, so whether is was a Accubond, Ballistic Tip, Corelock, Deadtough, E-Tip, GameKing, Hawk, Interbond, Loinload, Monolithic Sold, Oryx, SST, TSX, VLD, Weldcore PP SN, or even an IED? They aren't going to just fall over dead every time on the spot. Some go feet, some might go a 100 yards or more? But a well placed shot can and does kill with authority every time, no matter what it was shot with!