275lb Squats x 20 Reps Video
 

Generally the smith machines have counter balanced bars so it probably isn't 275lb.

Anyway, why use a machine to squat?

IW

The reps that you did after you said "5 more", your knees began to float inwards. That is how people hurt their knees squatting, I would be careful.

And yes, if you're on the smith machine in my opinion you may as well be leg pressing.

An accomplishment still, you're a big guy, all I'm saying is it might not go so well if you did it free weight.