All due respects to Mel Gibson's screen writers.
You get bum rushed by six people chances are you won't have time to pull the trigger more than twice.
I'm definitely on the down side of life's ladder yet I can run and shoot very well. I have practiced several techniques of Sweat'n'bullets fluid threat response. One in particular has you shooting while running at full speed back wards with good combat hits very achievable (i plan on one day actually taking the course). If bum rushed this technique could buy you the time needed to engage many more targets than either stand and deliver or the traditional back pedal while shooting.
On a side note even if you aren't able to move due to injury, age, or surroundings you can make subtle movements that will buy time such as a simple sit/roll to your back. Anything that buys you distance/time means more lead flying and increased odds of survival.
While I enjoy Mel's movies I understand that they are make believe. However I have run mock drills with friends simulating being attacked by multiple foes and using different responses to fend off the attack. Similar to FOF except without the force. It didn't matter in what direction I ran I was always able to point and fire at every attacker every time (3 guys was the max we ever had rushing but it wouldn't have mattered much if it were more).
I learned that the group usually strung out in a line as the faster or more aggressive powered forward. If my trigger pulls amounted to hits the leader of the pack would be hit multiple times if needed before he could reach me. If he fell he would be an obstacle slowing the others down further increasing my time. So I believe a bum rush can be survived provided you are able to employ the correct tactics and get good hits on your foes.
Thing is, I doubt most people will bum rush you once you pull a gun on them.
I agree. Still better to be prepared for as much as possible.