I'm not particularly refuting that, I'm refuting your character's ability to know the Mech had targeted it (or done anything) and dodge accordingly. By the time the sound waves registering the rifle moving (even this is sort of a leap, it suggests the Pater had absolutely no faith in its camouflage and prepared to evade the moment the Mech made any moves with its rifle, unless it were somehow aware the Mech had a very specific vision type perfect for cold blooded vampire xenomorphs) arrived the bullet would already be there, for previously mentioned reasons. I'm not saying the attack is unavoidable, but rather that the method you chose is both unrealistic and scientifically improbable. Similar to when DJ used the rationale that his character in the tournament heard a bullet fired and dodged accordingly, when it would simply have been more effective to say he saw the trigger being pulled. Sound is slower than light, which is why at extreme long range your character is at a disadvantage due to its sightlessness and reliance on Echolocation. Interesting you chose to fight at such extreme range, considering. 

It's of particular importance as your character seems to have already figured out how to avoid the Electric vision as well. If Higan can't score even a glancing hit first to convince him it's even possible to bring it down he'll probably just head home and bring in a heavy squad with flamethrowers. 

If you want to get -really- mathematical about it, though the general gist is sufficient in my opinion.

1. Higan adjusts and fires, which as my sheet says takes 0.20 seconds
2. Bullet fires towards targets pre-determined location taking around 1.2 seconds, add on the 0.20 of adjustment in Pater's favour, sound waves bounce back off turret pointing in the Pater's general direction
3. Bullet arrives up to three times faster than the sound waves, which take up to five seconds, dictating the Mech's movements.

So how has the Pater managed to use information from those sound waves to pre-emptively avoid the attack?