Well, the guy did it in real life is wrong. the armchair generals say so 
It was a complte waste of time, even though it apparently was a teached tactic when dealing with armor.. but thats ok, the AH model has it right, 50,000 rounds of 50 cal wont even scratch a tiger.. after all, what do the people who did it in real life know anyway... pfft, very little compared to our panel of video game experts. 
oh yea, from what ive read the tiger had 25mm of top armor, and 20mm of bottom armor... but dont let that get in the way of your assumptions.
Read some actual history.
In post action studies of German tanks knocked out by aircraft the RAF found two that had been destroyed by 20mm cannons. All the rest were done by bombs and rockets.
Next, try using some brains. In order to bounce bullets off the roadway and have them ricochet under the tank the angle is going to be very, very shallow. So, you have a tumbling .50 cal round that has lost energy in the impact with the ground hitting the bottom armor of the tank at an angle of no greater than 15 degrees and you think that has a chance in hell of penetrating?
Pilots reported and were told all sorts of false things. My grandma got angry and offended when I told her there were no arrows pointing at Pearl cut into the cane fields. I watched one WWII training film that instructed US soldiers not to worry about the menacing sound of the MG42, a gun with a rate of fire so fast you couldn't hear the individual rounds fire, telling them its bark was worse than its bite.