The Jarmann M1884 fired a 10.15 mm black powder cartridge in an 8-round, tubular magazine in which the rounds were lined up in a tube below the barrel.

However, this action is not considered strong enough to fire modern ammunition, since the only locking is provided by the rotating bolt handle.

Jacob Smith Jarmann designed his first breech-loading rifle—firing cardboard cartridges—in 1838,[2] but this was turned down by the armed forces at the time.

During testing to determine the correct graduation of the sights the rifle commission used improved ammunition, which increased the muzzle velocity to about 485 to 500 m/s.

The rifle commission found that the Jarmann with its 10.15 mm bullet had a maximum point-blank range of 438 metres (479 yd) with a 1.8 m (6 ft) target.

This compared very favorably to the Remington M1867, then the Norwegian standard weapon, with maximum point-blank range of 300 m (330 yd) and spread at 600 m of 96 cm (38 in).

From the mid-1920s and until the German invasion of Norway, it was possible for civilians to buy surplus Jarmann rifles for about a quarter of what a brand-new Krag–Jørgensen would cost.

In 1936 King Ibn Saud from Saudi Arabia initiated talks to buy 20,000 Jarmanns with ammunition for his police force,[2] but the request was turned down by the Norwegian parliament, who claimed that the sale of such outdated weapons would reflect badly upon Norway.

In 1938 a private investor — Trygve G. Hygen, a former captain in the Norwegian Army — caused a minor international incident when he offered to sell Jarmann rifles to Ceylon.

Attempts were also made by Hygen to sell Jarmanns to Lithuania, Cuba, Nicaragua, Bulgaria, Italy and the Netherlands, but without any takers.

[2] Some reports indicate that the Germans melted a significant number down[2] the last remaining Jarmann rifles in military warehouses during the Nazi occupation.

Between the wars, several Norwegian gunsmiths attempted to create harpoon guns,[2] intended for hunting seals and shooting rescue lines to boats in distress.

Seeing a ready market, and having access to the several thousand Jarmanns in storage, Kongsberg Våpenfabrikk designed a harpoon gun referred to as the M28.