The .416 Barrett was designed by Chris Barrett, son of Ronnie Barrett. The .416 Barrett is a large-caliber, centerfire rifle cartridge, designed to improve on the long range ballistics of the .50 BMG cartridge. There are quite a few very-low-drag bullets in production, and the .416 Barrett borrows heavily from them. It uses a 400-grain bullet and a case with 200-grain capacity. The case length is 3.27 inches and the overall length is 4.58 inches.  The .416 Barrett has the same case head dimensions as the .50 BMG, so with the exception of the barrel, almost every part of a .416 Barrett rifle is the same as a .50 BMG rifle. This is helpful because Barrett could avoid the tedious process of redesigning rifles around the new cartridge.
Barrett Firearms currently offers the Barrett M82A1 and Barrett M99 in .416 Barrett. The M82A1 in .416 Barrett comes with a bullet button which requires the use of a tool, such as a bullet, to access the magazine, therefore not making it a 'detachable magazine' and making it California legal. 
The use of a lighter, narrower bullet results in a significantly higher muzzle velocity and superior ballistic performance to the .50 BMG, and the .416 Barrett is claimed to retain more energy than the .50 BMG at distances over 1000 yards (914.40 meters). Barrett claims this cartridge is capable of propelling a 400-grain solid brass boattail spitzer bullet out of the 32 inch (810mm) barrel of a Barrett M99 rifle at 990 m/s (3250 ft/s), giving it a ballistic coefficient between .943 and .989 and keeping the projectile supersonic out to 2286 meters (2500 yards). The .416 Barrett takes 2.5 to 2.6 seconds to reach 1830 meters (2000 yards) compared with 3 seconds for the .408 Chey Tac, though it is not as accurate as the .408 Chey Tac.
The .416 Barrett lives up to its extreme long range potential. The gains in energy, flattened trajectory, and an uncanny ability to slip the wind are unmatched by other long range cartridges like the .338 Lapua Magnum and .50 BMG. The only other cartridge that comes close is the .408 Chey Tac. 
However, for its superior ballistic performance, the .416 Barrett cartridge burns up barrels faster than the .50 BMG due to its higher twist rate.
A few jurisdictions in the United States, most notably California, as well as a few nations such as Australia, Belgium, Italy, the Netherlands and Poland restrict or prohibit civilian ownership of rifles chambered to use the .50 BMG cartridge, but not the .416 Barrett.