http://www.intuitor.com/moviephysics/The Mac 10 Problem
"Although 9 mm submachine guns such as the Uzi (which fires 600 rounds per minute) are popular in movies, everyone knows that real action heroes prefer .45 cal Mac 10's. These fire bigger bullets at rates of 1000 rounds (in other words bullets) per minute. They have a thirty-round magazine (the long black thing that stores the bullets) and are by any measure a deadly weapon.
Movies are filled with scenes of good guys and bad guys blazing away for minutes at a time. Of course, no one is overly concerned with reloading or lack of ammunition, but then that's been true since the days of singing cowboys such as Roy Rogers who smiled a lot and engaged in friendly gunplay between musical numbers. So why would we bother to mention what is common knowledge? We can't help but be impressed by the weight of the matter.
First, let us point out that the thirty-round magazine in a Mac 10 will be expended in a mere 1.8 seconds of sustained fire! If our shooter blazes away steadily for a total of only 3 minutes, his or her Mac 10 will spit out around 3000 chunks of lead at roughly 15 grams a piece. This amounts to 45 kilograms or a little less than 100 pounds of lead. And that doesn't account for the weight of the 3000 cartridge cases or 100 empty magazines scattered on the ground.
Second, bullets are, after all, propelled by some very hot gasses which exert high pressures that create high stresses in gun parts. A firearm can withstand the high pressures and stresses only if the blasts of high temperature gasses don't happen too many times before the firearm has time to cool off. Running 3000 of these temperature cycles back-to-back would turn a light weight submachine gun, like a Mac 10, into a red hot piece of scrap metal, that is, if it even lasted for 3000 rounds.
Yes, 9 mm submachine guns with slower firing rates would reduce weight problems, but it seems that real action heroes use Mac 10s, preferably one in each hand. We can't help asking where the sidekicks are with wheelbarrows to carry the ammo, let alone the cooling systems."
Hollywood and newspaper writers seem to have alot in common.