1-11s in the 300 WSM
are setting the house afire all the time with 210s
Only reason seirra lists the 240 at 1-9 is because it was developed for LR NRA shooters (actually Army MTU tested them) shooting med velocity as a replacement for the old 250 years ago. They needed the extra twist for the lower velocities. Step up the MV and shoots great in 1-10.
187 grainers are being shot in record groups out of 1-13 and 1-14 in the 300 Ack Imp all the time.
Needed twist can be adjusted up or down by MV. 300 Weatheby has zero problems hammering 240s in little tight groups out of 1-10.
Do not fall trap to assuming all 30 calibers shoot best with a 1-10, when in reality you have to be a little smarter than that and figure the expected MV into the equation.