It?s amazing how James can ask such a simple question and have it result in such a loooong thread and passionate exchange. I have stayed on the porch so far on this thread as I am a relative small pup in the field of big dogs that are sharing their experiences and opinions.
Getting back to the original question I would define bullet failure as a projectile that either fragments prematurely without imparting a fatal wound on an animal or a bullet that penetrates without making a sufficient wound channel to quickly kill or immobilize an animal. Penetration is great but obviously controlled expansion will kill quicker if the penetration is adequate. It?s my preference that a bullet creates a larger than caliber would channel and always exits to create the best possible blood trail if the animal does not drop. Additionally, bullet placement and using enough gun are baseline requirements for properly judging a bullets performance. The rules certainly change as the game gets bigger. So another important rule is to properly match the bullet and cartridge to the game. I have taken about 20 whitetails with various 44 magnums using 23 grains of H110 with a 240 grain Hornady XTP. All have been pass throughs with 0 bullets recovered. For me this round works great on deer. I have shot 2 whitetails with SSK 320 cast bullets and both ran some distance with double lung shots. If I were to use the 44 Magnum on larger game I would consider the 320 cast or possibly a tougher jacketed bullet. I have shot about the same number of animals with the TC 358 JDJ that have also all been pass throughs. About 10 deer with the Speer 220 grain flat point and about 10 or so with the Hornady 250 grain Interlock. Again all pass throughs. Velocity of the 358 is about 2000-2100 at the muzzle. The largest animals I have shot with this bullet is a 600 lb Kudu and a 450 lb or so Blue Wildebeest plus a couple warthogs. All full penetration shoulder shots. The Kudu at 190 yards and the Wildebeest at 100.
I consider the Speer 220 flat point the best 358 deer bullet and the 250 Hornaday spire point a great bullet for larger game up to Moose or Eland. It is my assumption that if any of these 3 bullets were driven at significantally higher velocities they may fracture and fail. Again I am sure the rules are different for the big bovines.