The Karabiner 98k was a bolt-action rifle with Mauser-type action holding five rounds of 7.92 x 57 mm (also known as 8 mm Mauser or 8 x 57 IS) on a stripper clip, loaded into an internal magazine. It was derived from earlier rifles, namely the Karabiner 98b, which in turn had been developed from the Mauser Model 1898. The Gewehr 98 or Model 1898 took its principles from the Lebel Model 1886 rifle with the improvement of a metallic magazine of five cartridges. Since the rifle was shorter than the earlier carbines, it was given the designation Karabiner 1898 Kurz, meaning "Short Carbine Model 1898". The standard Karabiner 98k iron sights could be regulated for ranges from 100 m up to 2000 m in 100 m increments.
The rifle was noted for its good accuracy and effective up to 500 meters (547 yards) with iron sights. For this reason, rifles selected for being exceptionally accurate during factory tests, were also used with a telescopic sight as sniper rifles. Kar 98k sniper rifles had an effective range up to 800 meters (875 yards) when used by a skilled sniper. Improvement beyond this standard was possible with the help of German Luftwaffe (Air force) 7.92 mm high velocity machine gun ammunition which achieved a higher muzzle velocity due to a more powerful smokeless powder charge. German snipers sometimes used this high velocity round to gain an extra 150 meters (164 yards) effective range and increased accuracy at closer ranges.
The 98k rifle was designed to be used with a S84/98 III bayonet and to fire rifle grenades. Most rifles had laminated stocks , the result of trials that had stretched through the 1930s. Plywood laminates resisted warping better than the conventional one-piece patterns, did not require lengthy maturing and were less wasteful.
The 98k had the same disadvantages as all other turn-of-the-century military rifles in that it was comparatively bulky and heavy, and the rate of fire was limited by how fast the bolt could be operated. Its magazine had only half the capacity of Great Britain's Lee-Enfield rifles, but being internal, it made the weapon less uncomfortable to carry. While the Allies (both Soviet and Anglo-American) developed and moved towards standardization of semi-automatic rifles, the Germans maintained these bolt-action rifles due to their tactical doctrine of basing a squad's firepower on the unit's light machine gun and possibly their problems of mass producing semi-automatic rifles.
In close combat, however, submachine guns were often preferred, especially for urban combat where the rifle's range and low rate of fire were not very useful. Towards the end of the war, the Kar98k was being phased out in favour of the StG44 assault rifle, which fired a round that was more powerful than that of submachine guns, but that could be used like a submachine gun in close-quarters and urban fighting. Production of the StG44 was never sufficient to meet demand, being a late war weapon, and because of this the Mauser Kar98k rifle was still produced and used as the standard infantry rifle by the German forces until the German surrender at the end of World War II in May 1945.
 Combat use
 World War II The Mauser Kar98k rifle was widely used by all branches of the armed forces of Nazi Germany during World War II. It saw action in every theatre of war involving German forces, including occupied Europe, North Africa, the Soviet Union, Finland, and Norway. Resistance forces in German-occupied Europe made frequent use of captured German 98k rifles. The Soviet Union also made extensive use of captured Kar98k rifles (and other German infantry weapons due to the Red Army experiencing a critical shortage of small arms during the early years of World War II) and rifle factories during World War II, as they were somewhat familiar with the weapon's technology after buying the licences and machinery necessary to manufacture them from the Nazi Germany during the time of the Molotov-Ribbentrop Pact. However most of these factories were converted to produce Mosin-Nagant rifles and carbines as Soviet forces gained stable territory and were able to establish supply lines for production. Many German Soldiers used the verbal expression "Kars" as the slang name for the rifle.
 Post-World War II During World War II, the Soviet Union captured millions of Mauser Kar98k rifles and re-arsenaled them in various arms factories in the late 1940s and early 1950s. These rifles were originally stored in the event of future hostilities with the Western democracies.
Most of these rifles were eventually shipped to communist or Marxist revolutionary movements and nations around the world during the early Cold War period. A steady supply of free surplus military firearms was one way that Moscow could support these movements and states without giving them the latest Soviet infantry weapons until these movements and states gained the trust of Moscow to warrant the supply of modern Soviet infantry weapons.
One example of the Soviet Union providing the Mauser Kar98k rifle (as well as other infantry weapons captured from the Germans during and after World War II) to its communist allies during the Cold War period occurred during the Vietnam War with the Soviet Union providing military aid to the armed forces of North Vietnam and to the NLF in South Vietnam.
A considerable number of Soviet-captured Mauser 98k rifles (as well as a number of 98k rifles that were left behind by the French after the First Indochina War) were found in the hands of NLF guerrillas and VPA soldiers by U.S. and Allied forces alongside Soviet-bloc rifles like the Mosin-Nagant, the SKS, and the AK-47.
In the years after World War II, a number of European nations that were invaded and occupied by Nazi Germany used the Mauser Kar98k rifle as their standard-issue infantry rifle, due to the large numbers of German weapons that were left behind. Nations like France and Norway used the Mauser Kar98k rifle and a number of other German weapons in the years after World War II. Firearms manufacturers like Fabrique Nationale (FN) in Belgium, Česká Zbrojovka (CZ) in Czechoslovakia (as P-18 or puška vz. 98N, the first being the manufacturer's cover designation of the type, the second official army designation - rifle model 98, N for německá - German) and the Zastava plant in Kragujevac, Serbia, Yugoslavia, continued to produce the Mauser Kar98k rifle after 1945 as M48. In Romania, the Czechoslovak version was known under the informal name of ZB, after Zbrojovka Brno - the Czechoslovak main state producer of small weapons and munitions (now closed) - and, since a large surplus of this version was available, it was used to arm Romania's Patriotic Guards, before sufficient numbers AKMs were available for them. From 1950 to 1965, Zastava produced a near-identical copy of the Kar98k called the Model 1948 (M48) which differed only from the German rifle in that it had the shorter bolt-action of the Model 1924 series of Mauser rifles. Yugoslavia sold many of these rifles to Algeria, Egypt and Iran during the 1950s and '60s. Many surplus M48s have been sold in the United States, Australia and Canada in recent years.
 The Persian Brno The Czechoslovak variant of the Mauser rifle found its way into Iran very quickly where it became known as the 'Brno', following the name of the city of Brno, Czechoslovakia where the rifles were originally manufactured. The Mauser rifle was selected for the Iranian Army during the reign of Reza Shah Pahlavi, however Iran never ordered any from Germany, instead preferring the Czechoslovak variant.