A neck shot on a deer is a dead deer on the spot every time. Never had a problem with it that wasn't caused by a poor shooting, in other words someone just missed what they were aiming at.
A neck shot to the middle of the middle of the neck will kill it outright, collect the spine, and all the major artieries, carotid and jugular will be taken out. Essentially you are decapitating the animal.
The higher up the neck the more it all converges into one vulnerable package.
Headshots should be avoided - neckshots enouraged. The neck is a much bigger target and it doesn't flick around and move quickly like the head. With the spine and arteries so close together in the neck you can consider the neck as one big vulnerable organ. I dont know why some people consider them 'iffy' or 'tricky'. (The only thing is a stags throat swelling in the roar and its hair will mean the spine is higher than you think.)
As a deer hunter you need to learn this shot, its a important part of your reportoire. The other one is the high shoulder shot (which essentially should be thought of as a spine shot that also destroys the shoulders as collateral damage.)
Both of these will drop the animal in its tracks without a death run, unlike lung shots or 'hilar' shots and so forth. A bullet in the lungs will kill a deer every time, but a neck or high shoulder shot will drop it right
here.
I can recommend "The New Zealand Hunting Rifle" book which describes this kind of thing.

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