JR Potts, AUS 173d AB and Dan Alex (Updated: 10/27/2016):
Origins of the Model 1898 could be traced back to its immediate predecessor, the Gew 88 (also Model 1888 or M1888). The rifle was quickly developed in response to the arrival of the new French 8-round Lebel bolt-action service rifle of 1888 - the first firearm in the world to make successful use of small bore smokeless powder ammunition. This development immediately rendering all other black powder guns obsolete and brought about a new era in firearms. In an effort to match their foe and long-time neighbor, the Germans utilized a committee approach to formulate the new Model 1888/Gew 88 to make use of its own brand of smokeless powder in 7.92x57mm cartridge form.
The Model 1888 held its bolt-action function within a single-piece stock which incorporated the butt, grip and forend. The magazine was integral to the design and projected through the bottom of the body as part of the trigger ring. Sights were located at center of the stock top and just aft of the muzzle while sling loops allowed for a shoulder strap. The bolt-action handle stuck out in the horizontal for quick access though this feature increased the likelihood of snags (addressed in future Mauser revisions). Consistent with the times was a mounting point for a field bayonet intended for close-quarters combat. Loading was by way of a Mannlicher-style "clip" system which required all 5 rounds to be fired before the magazine could be accessed, the clip dropping through the bottom of the rifle. The rifle managed an existence throughout World War 1 (used in a frontline role until 1915) but was seemingly lacking many of the frontline qualities required of a service rifle - proving generally unsuccessful and something of a failure - partly due to the all-new ammunition in use and the lack of a single-loading/topping off capability of the magazine. The outgoing rifle was then pressed into service with Austro-Hungarian and Turkish forces after the Germans abandoned it in favor of the newer Gew 98.
Development of a new service rifle managing the same 7.92mm ammunition (with greater powder charge) spurred the Model 1898/Gew 98 into being. The Gew 98 weighed in at approximately 9lbs (4.09kg) and was 49-inches long (1,250mm) overall with a 29-inch (740mm) rifled barrel. It was fitted with an internal magazine holding five cartridges and fully held within the receiver. With the soldier in mind, the rifle was designed to incorporate two sling swivels for a shoulder strap, useful in transport of the gun by infantry or helping to sight the rifle on a target. The two swivels connected on the bottom of the stock supported a leather sling, but as the war dragged on the slings were made out of canvas. The rifle made use of an open front sight post and a tangent rear sight mounted perpendicular to the line-of-sight (LOS). This open-wide aiming sight was designed for field use in all levels of light and for a quick-shooting action against large targets like men in units or groups at ranges from 200m to 2000m in 100m increments. The Gewehr 98 had an oil finished rifle stock with a slight pistol grip made from walnut. Though a highly-effective and efficient weapon, the Gewehr sported the negative found on most other turn-of the century rifles - she was simply too long to be used effectively in close-quarters. Where trench warfare ruled the battlefields of World War 1, the rifleman could quickly be assaulted at close range by his enemy. The Gewehr could become a liability in such combat. In end, however, the Gew 98 proved a robust, accurate and excellent weapon system.
Every combat rifle was designed to use the weapon of last resort, the bayonet. The Gewehr 98 had a top barrel clip with a 4.5-cm (1.75-inch) long bayonet lug. The advantage of using the clip instead of muzzle rings increased the firing ability of the rifle. The rifle was originally issued with the Seitengewehr 98-type bayonet, itself a 500mm (19.8-inch) long quillback blade. This bayonet was found to be too long for trench close-quarter combat. By the end of the war, this bayonet was replaced with the 10-inch Seitengewehr 84/98 blade introduced due to German soldier complaints fighting in narrow trenches.
The heart of the Mauser M98 bolt-action system was the bolt itself. A new larger and stronger receiver design became the U-shaped shroud that held the controlled bolt group, itself having three locking lugs. Two larger main lugs were fitted to the bolt head while the third lug was used for safety at the rear of the bolt - essentially a redundant lug if one of the first two lugs had failed. The third lug was the unique feature not seen on the previous bolt-action models. The bolt handle was straight with a round knob on the end and attached directly (and permanently) to the bolt. The firing pin striking the primer on the bottom of each cartridge ignited the cordite and fired the bullet. The firing pin was cocked when the bolt was opened by the operator. Working against the M98 was the fact that it was not an easy component of the rifle to mass produce in number.