I've read somewhere before that bang flops depend on the timing of the heart when the bullet hits. I may have it backwards, but it was along the lines of if the heart is contracting in then they can run after being hit.
If they are hit while the heart is pumping blood out then it sends a pressure wave through the blood vessels which rupture/do all kinds of damage instantly to the nervous system and they fall over.
Obviously this is for a heart area shot where a shockwave will put pressure on the heart, head/spine/other shots are on their own for this theory.
This is true. The same physiology is at play when a hockey player gets hit in the chest with a puck and it stops his heart. It happens, but it's rare. my results hunting deer indicate there is a 5-10% chance of this result. I mainly use bonded bullets.
Some like to use 'frangible' bullets for deer - they provide a greater peak energy transfer, but IME relying on hydrostatic shock for bang flop is ill advised. the ballistic tip used to be one of those, but the design was modified recently - it now sports a thicker jacket, and holds together better than it used to on impact. I have seen bang, flop, but then the deer gets up and runs 100m.
The most reliable 'bang flop' results come from disrupting the upper CNS - I've had pretty consistent bang flops when targeting the base of the head - gotta be close, and the deer must be still. I do not recommend head shots, but I do take them when conditions are perfect. Bullet construction does not seem to influence the gruesome result here.
Statistically, Remington core-loks are at the top of my list for bang flop results, but I am confident bullet placement has more to do with it than the 'magic of the core-lok'. Placed through the upper shoulders/base of the neck they are very effective but result in turning 10-15% of the deer into dog food (bloodshot).
OP I think you might do well to carefully define 'good placement'. In my experience there is no magic bullet, but there certainly are a couple of 'magic locations' that will drop a deer on the spot when a bullet is placed there.
These days I favour avoiding the shoulders when harvesting deer - if I need some margin of error, low through the lungs is where I point.