shaman,
One theory is that flat-based cup-and-core bullets tend to retain their cores better than boattails. That was even promoted by some gun writers, back in the day when most big game hunters used cup-and-cores, rather than pay for expensive "premium" bullets like Nosler Partitions.
I used to think this too, when I didn't have much experience, after seeing a 130-grain Sierra GameKing .from a .270 Winchester lose its core upon hitting the ribcage of an eating-size mule deer buck at 100 yards. Found the jacket just inside the entrance hole when skinning the deer, but the core kept penetrating and killed the deer.
Years later, when I had several hundred big game kills recorded in my hunting notes, both mine and hunting companions I'd been standing beside, I analyzed the results and found that just about the same number of boattails and flat-bases had lost their cores.
Some rifles don't shoot boattails well, but in my experience very few. Probably this is due to a slightly large-diameter chamber throat allowing powder gas blow-by.
Thanks for the quick come-back.
In years past, I regularly substituted BT's when I couldn't find FB's. Internet sales pretty much did away with that, but now I see shortages causing one to think about things on a make-do basis.
I can't say I've had an instance of bullet failure with either, but then my habits are pedestrian.
