I suspect my 99 somehow got out of the factory with a slightly slower than 1/14 twist, only bullet it will group is the stubby little Sierra 90 grain HPBT.
I once owned an older .250 99 that would NOT shoot any of the usual 100-grain bullets worth a hoot, even though I live at 4000 feet above sea level, including the 100-grain Hornady Interlock and Speer Hot-Cor.
Finally I measured the twist with a cleaning rod, and it turned out to be 1-15. This sort of variation wasn't all that unusual back when most rifle manufacturers used sine-bar cut-rifling machines, which were adjustable for twist. So I tried the 87-grain Hot-Cor, and all of a sudden the rifle shot 1" groups.
