I have come to the belief that the Ballistic Tip hit bone and failed to penetrate.
Several of the BT's have evolved over time. Jackets have been thickened, toughened for specific applications. So, the bullets you have today may not be the same when you buy them again. Unfortunately, Nosler doesn't publicize the information when the changes are made. We have to learn of it "at the back fence."
Like you, I have settled on the Accubond and have two lifetime's supply of what I shoot. Thus far, I have taken numerous animals with them and have yet to question them for any reason.
