It seems that all the crappy performance I ever had on deer were with boattail bullets. Hornady's 140gr. BTSP was especially bad, along with Sierra's Gamekings. I know, after I switched over to flat-based bullets, my problems all went away. I've had good performance with some boattails, but then bullets out of the same danged box would explode and crater on the deer.
Some folks swear by those 140 Hornadys (.277"), but I'll never use them again. Gamekings are hit or miss, sometimes they'll do the deed just right, and sometimes they don't.
For whatever reason, I've never been able to get Speers to shoot worth a hoot.
Funny enough, the two bullets that I have had the worst luck with were both Speers. One was the 6.5mm 140gn that would not shoot in a vary accurate Mauser M12 6.5x55 that shoots every other bullet very well. The other was the 7mm 145gn Grandslam that shot three inch plus groups in a very accurate 7x64. I tried the Grandslam in another 7mm rifle, my Number 1 7x57, and same result. That rifle is a 1.5 inch rifle but no luck with the Grandslams.
But the only bullet that ever put three into the one hole was the Speer .30 cal 165gn BT from my .30-06 at 100m. That was a undoubtedly a fluke as I never did it again but that bullet did shoot just under the inch. Despite the bad luck with the 6.5mm 140gn, the Speer 6.5mm 120gn shoots brilliantly, as well as the 120gn Sierra, Ballistic Tip and 129 gn Hornady. Speer have given me the most inconsistent results from all the bullet manufacturers, whereas Noslers, Hornadys, Sierras etc have all shot well enough to be acceptable for hunting. Maybe some of Speer's machinery is getting old or something?
