Dear gun toting reporter-
I will refrain from the temptation to club you for incipient grossly irresponsible journalism, in the hopes of possibly educating you.
Contrary to poorly researched information falsely presented as fact in the media, in the US, you have not been able to buy an ACTUAL firearm THROUGH THE MAIL since 1968. That is when the Federal 1968 Gun Control Act went into effect. To do so is a Federal crime that will put you in prison for a VERY long time. See US Code, Title 18, section 922.
You found a website that sells replicas. In other words, a model of a gun. But not a gun. If you found a website that sold models of the F-16 Jet Fighter, you would not assume that all F-16s were made of plastic, and were 11 inches long, would you?
With the POSSIBLE exception of the the legal sales of narcotics and nuclear fuel rods for a reactor, firearms are the most stringently LEGALLY regulated commodity sold in the US.
While the .44 Remington Magnum is a large, powerful (and real) handgun cartridge, it is NOT the "most powerful handgun in the world". Not even back when they made the movie. And your website also got that wrong- the replica shown is a .357 magnum- not the 44 Magnum referenced in the movie. It is also a model of a Colt Revolver- Harry Calahan had a Smith & Wesson.
Now, when you are looking for actual information, please come back by. I will do my best to give you a straight answer, and not call you names. While you HAVE been thoroughly pelted by the folks here, you DID give them cause.
Link to information on the real thing- .44 Magnum - Wikipedia, the free encyclopedia