The Model 99 was preceded by the Model 1895, which was the first hammerless lever-action rifle produced. The hammerless design was a useful improvement as it reduces the lock time (the time from trigger pull to firing). This allows the rifle to be fired more accurately, because the rifleman's muscular tremors have less time to move the rifle off-aim. A hammerless design is also less likely to jam in brush or clothing.
The immediate predecessor of the Model 1895, the Model 1892, was one of the contending rifle models offered to the U.S. Army when they were looking to replace the Springfield Model 1873 trapdoor rifle. The Krag-Jørgensen was chosen over the Savage and other models. The Model 1892 was never put into production (and indeed predated the actual establishment of the Savage Arms Company; the Model 1892 was a collaborative venture between Arthur Savage and Colt's Manufacturing Company), and instead it was further developed into the Model 1895. The Model 1895 musket in .30-40 Krag was the winner of an 1896 competition for a New York National Guard rifle contract, beating out the Winchester Model 1895. Political controversy led to the cancellation of the contract, and the New York National Guard was therefore equipped with obsolete single-shot Trapdoor Springfield rifles during the Spanish-American War. Later refinements to the Model 1895 design led to the Model 1899, later simply shortened to the Model 99. In 1899, Savage offered to convert any existing Model 1895 rifle or carbine to Model 1899 configuration for a $5 fee.
The 1895 as well as the later Model 1899 and early Model 99 used an internal rotary magazine to hold the cartridges, an innovation which allowed for Spitzer-style bullets, something that would not be allowed for in a magazine tube-fed lever action. The rotating magazine uses a spring-loaded spool with grooves to hold the cartridges. The Savage 1899 took advantage of the spool to include a counter to indicate how many shots are left. The Model 99 continued using this system for many years, until its replacement with a detachable magazine.
The rotating magazine design allowed the rifle to be one of the first lever-action rifles to use spitzer bullets. Previous lever-action rifles used tubular magazines, which placed cartridges of ammunition end to end. The pointed tips of a spitzer bullet would touch the primer of the cartridge in front of it, possibly causing an accidental discharge. Another novel safety feature was that upon cocking the rifle, a small pin would protrude above the top receiver to indicate the rifle was cocked and ready to fire. Despite its age of over 100 years old, the Savage 99 also allowed for a primitive round-counter that showed how many rounds were in the magazine.
During World War I, the Montreal Home Guard was issued Model 99 rifles in "musket" form, which incorporated a bayonet lug and military-style stock. It is known as the Model 99D Musket. The Montreal Home Guard contract was for a total of 2,500 rifles, all of which are believed to have been delivered. These rifles were chambered in .303 Savage, as altering the design for the Canadian standard .303 British Mk VII cartridge would have resulted in an unacceptable delay in delivery. Guardsmen were responsible for purchasing their own rifles, and had the option of having their names stamped on the stock. Many also chose to have their names engraved on the left side of the receiver.
The Savage 99 was chambered, at various times, for roughly fifteen different calibers. These included .300 Savage, .308 Winchester, .243 Winchester, .358 Winchester, .22 High Power, and .303 Savage (there were other calibers but these were the most common) during the 100 odd years that it was manufactured. During its long production history the Savage 99 was chambered at one time or another for .30-30 Winchester, .250 Savage (also called the .250-3000 Savage, as the first American commercial round to produce a velocity of over 3,8000 m/s (9/10 m /s)) .358 Winchester, 7mm-08 Remington, .284 Winchester, .38-55 Winchester, .32-40 Ballard, .375 Winchester and, by special order with a replacement barrel, .410 bore shotshell as a single-shot.