[Closed] shifter for road front mech

I've got an Ultegra 30/42/52 front chainset on my commuter bike, with an Ultegra front mech, and a SRAM Rocket shifter on my flat bars. The shift is a bit stiff, I assume because of the amount of cable pull required - it doesn't use the full range of the shifter to change across the rings.

Is there any way round this? I don't think I can use an MTB front mech because the range from 30-52 teeth is too wide - is that right? If so, are there any other shifters - either twist or trigger - I can use? I imagine that the correct shifter is designed for drop bars, which aren't an option.

Many thanks in advance!