Are you applying for MBA or PHD program?
My experience is that GMAT is not the decisive factor if you are a qualified candidate for McGill's PhD program in management.
GMAT over 700 is enough, I think.
A match between faculty members and you is more decisive to be admitted to the phd program if you could enter the short list.
hope it is useful.
Good luck.
I have gotten the offer from McGill University Faculty of Management. GMAT:700; TOEFL: 273; 10 years experience as an engineer and manager in media industry.