7mm Ballistic tips and Accubonds

It's been my experience that the AB bullet opens up nicely on WT deer. I use the 250 gr AB in my 338 RUM for crop damage deer hunting and the exit wounds are typically the size of a golf ball. Most of the deer taken are does that weigh 100-120 lbs. at ranges of 50 yards to 600+ yards.

While you state that both deer were shot in the same spot, with two different bullets, you have not noted whether the bullet placement was exactly the same on both does...by this I mean, did one enter through a rib, while the other entered between the ribs, as this can make a difference in the expansion of the bullet and how quickly the shot will be lethal. Did one impact heart and lungs, while the other only impacted lungs?
What were the states of awareness between the two deer? Was was one alert, whereas the other was not? This too can have an impact on how the deer react upon being hit.
As noted above, the state of the lungs at the moment of bullet impact can also have an effect on how the shock impacts the animal and its organs. Lungs full of air will react differently than when the lungs are empty at the end of exhalation, and the resulting damage to the lung tissue.
Did either shot clip the heart?
A heart shot animal will react differently than a lung shot animal. When an animal that has received damage to the heart, the brain release endorphins that causes the surge in energy that makes these animals run (death run), and this may be the difference you witnessed.
And just as no two people are alike, the same goes for animals. Each has its own measure of tenacity that cannot be judged equally from one animal to another. Some lay down and succumb to relatively minor wounds, while others take a licking and keep on ticking from several vital hits.

There are so many variables that need to be accounted for, before laying blame to a bullet's failure, or success, that it is difficult to use a single scenario as a representative sample for judging one bullet's performance against another.
At the end of the day, you successfully harvested both animals and have supplied tablefare for you and your family. From this standpoint, there was no failure.

There is a common myth out there that animals properly hit should be DRT. Unless hit in the spine where the spinal chord is cut or severely damaged from the shoulders forward, or a brain shot, they will not usually die in that spot. Most animals will run from a central body hit. And as stated above, will definitely run if hit in the heart. Close range shots also see most animals run from the sound of the shot as well.

I have used both bullets on a wide variety of game, in a variety of cartridges/calibers, over the years, and both have done well, as long as I have done my part. I would not hesitate to use either on big game. I will say that I do prefer the AB, as it does provide better penetration on larger, heavier game than the BT. I have used BT's on moose (e.g. 270 Win while deer hunting) , and AB's on antelope (7MM STW) with great success. If I do not want the animal to run (such as a moose close to water, or an elk close to a ravine, or a sheep close to a cliff) I will take the high shoulder shot to immediately immobilize the animal. Otherwise, I go for the double lung shot to shorten the tracking job, and avoid the heart so that it does not run as far on the surge of adrenaline.
I wouldn't blanket ABs based on a sample of one. If you deer hunt long enough, stuff happens. My brother shot a nice buck one year with his 308 Win and a 150 Ballistic Silvertip. That deer ran 100 yards and almost made it onto a neighbors property.....and there were chunks of lung on the ground where he shot it. That actually soured him on that bullet, even though IMO, hard combo to beat for deer.