League-of-legends – What happens when you ult a champion with a global ult

When Xypherous did his Dev Diary for Nautilus he answered this question:

(Forum Goer)Quote: Can you dodge it, or blink over it (referring to the ultimate)?

(Xypherous):If you doge it or blink over it, it will turn around to chase you some more, forever - RUN SINGED RUN.

(Forum Goer) Quote: Master Yi Speed Test Inc.

(Xypherous):I think Rammus stands a better shot of making it halfway across the map before it hits him - :P

(Xypherous):If you can outrun it for 5 seconds or get 2000+ units away from it, it'll just explode on the spot.

Link to the source

Found a video of someone actually managing to outrun Nautilus' ultimate:

Short answer: NO.

Long answer: The mechanic of Ace in the hole is: If you have vision of the opponent you can use the skill, when the skill is used you WILL fire the shoot.

The only way is to some ally enter in front of the shoot and take the damage. OR you kill Caty BEFORE she fires at you.

Ace in the Hole (Active): Caitlyn marks an enemy champion at a huge range and channels for 2 seconds to line up the perfect shot, providing vision of the target for the duration. She then fires the projectile to deal massive physical damage. Enemy champions can intercept the bullet for their ally.