I am losing town line sprints with my midweek cycling group largely it seems because my front derailleur (all 2x9speed Dura Ace with clamp on FD) refuses to shift up to the big ring when I really need it.

at moderate speed and light load, she shifts like a dream.

But when Bill jumps and I want to respond and start to chase him down (and so I am already spinning the pedals fast) but need more speed), she balks.
and even dropping it down to a 12t but on the small ring, I can't get enough speed.

what suggestions?
is it my sprint-shifting technique? (I am a no nothing on race tactics)
or could there be a mechanical or setup issue?

Many thanks

Peter