The Standschütze Hellriegel 1915 is a water-cooled submachine gun produced in very limited numbers for or by the Austro-Hungarian reserves (Standschütze) during World War I, by a designer identified only as "Hellriegel". The weapon could be fed from either box magazines or chute-fed.
A highly obscure weapon, no complete examples are known to still exist, and little official documentation remains. As a result, its operating mechanisms, exact production numbers and development history are all based on speculation. However, photographic evidence exists of it in live-fire tests which are dated October 1915, making it one of the earliest submachine gun designs in history. It is unknown why the weapon did not progress beyond the prototype stage. 
The weapon is portrayed in Battlefield 1 with a fictional magazine attached to the weapon itself. The magazine slides in and out of the magazine well, and is locked and unlocked by manipulating a lever present on the front of the weapon.
— In-game description
A Hellriegel 1915 Storm variant, equipped with a Buckhorn Sight, assumedly reduced recoil and increased zoom, can also be found in a crate in the War Story, Through Mud and Blood.
— In-game description
The Hellriegel 1915 Factory is unlocked upon reaching rank 10 with the Assault kit. The weapon's high magazine capacity of 60 rounds makes it extremely effective against enemies in close quarters compared to other submachine guns and LMGs. Despite this, its relatively moderate recoil makes it somewhat difficult to engage enemies at longer ranges unless controlled bursts are fired. It also overheats after 40 consecutive bullets.
The Hellriegel comes equipped with 180 rounds of ammunition (60 rounds loaded in the magazine and 120 carried in reserve).
— In-game Description
The Hellriegel 1915 Defensive is a weapon variant introduced in the Spring 2017 Patch. It is unlocked upon completion of the correlating assignment which involves obtaining 300 kills with the Factory variant and 25 kills with Anti-Tank Mines. Unlike the default variant, it features a Bipod, an Extended Magazine holding 120 rounds and a Lens Sight. Consequently, it features much higher recoil.
- A glitch in the class ranking system allowed players to purchase the weapon before being level ten in the Assault class. This was due to the system incorrectly tracking values higher than what was intended. This was fixed in a patch but allowed players to keep the weapon if already purchased, even if the rank 10 criteria had not been met.
- A glitch associated with the February 2018 Update, released alongside Battlefield 1: Apocalypse, resulted in the sights of the Hellriegel not being visible. 
- The Hellriegel used to have only 120 rounds (translating to 60 loaded and 60 rounds carried in reserve), but after the Spring 2017 Patch, it was increased to 180 rounds (translating to 60 rounds loaded and 120 rounds carried in reserve).
- A faint water sloshing sound can be heard while moving with the Hellriegel. This presumably comes from its water-cooled barrel.
- As the Hellriegel has no known surviving examples, and all photographic evidence only show the right side of the weapon, the weapon's left side shown in-game is entirely based on conjecture and artistic license (due to the fictional magazine).