As Rachel was saying on the show yesterday (video), the .50 caliber bullet is a different kind of deal. The inventor of the round and weapons to fire it marketed one of the guns this way, in a 1980s brochure:
The cost-effectiveness of the Model 82-A-1 cannot be overemphasized when a round of ammunition purchased for less than 10 USD can be used to destroy or disable a modern jet aircraft.
The .50 caliber is legal in every state except California. Last month the New Jersey legislature voted to ban .50 caliber rifles. The bill is now sitting on Governor Chris Christie's desk. He has not said whether he will sign it.
While I was looking around yesterday for video of people using the .50 caliber -- it's a favorite of big-gun enthusiasts -- I found this old clip labeled "Guy hit in head with .50 caliber ricochet." The good news is that he survives in great shape. But watch how quickly he and his friends swear off using the .50 caliber (or adding, from @That_One_Guy_in_WA: "shooting it at iron targets").
Thanks to the Illinois Council Against Handgun Violence for the old Barrett Firearms brochure. Rachel's segment from last night is after the jump.