I was on GR3's as a techy and seem to remember there was a slam check before take off where it had to go from idle to 95% in two seconds. I'm sure bona mates on here will put me straight but I don't think I'm far off.
I was also the GR3 and you are not wrong about the accel times. It wasn't just the speed of the thing, its was the severe vibration (with the nozzles aft) which meant that it was hard to read the RPM gauge, let alone nail it on the stopwatch.
Remember the "max bleed wet" slam? Water on, full rudder with left leg, right leg wrapped round the stick pulling it full left and aft, left hand slamming the throttle and right hand on the stopwatch. It was rather challenging but fun
