Bow Weaponry
In the Grimdark future of the 41st Millennium, simple bows and other archetypes is still somehow in use in the far future. Although the majority of bow and other string weapons are obviously ineffectual to the battlefield of the 41st millennium, there are a few that still find use within the Inquisition. By far one of the most 'advance' bow weapons (Advance being put in the lightest sense of the word) is the Crossbow. A crossbow when combined with modern materials and techniques, can be comparable to modern weapons in terms of damage infliction. They are not very common in war, but are sometimes seen with rebellious street gangs or irregular troops. Often they are developed with an automatic draw mechanism which allows for much faster reload, but it is impossible to move and reload at the same time, making it a cumbersome weapon.
Types of Bows
Bow
The most primitive and common of the Bow family. The simple Bow is found on almost every planet as a hunting tool and rarely a weapon of war.
They are simple enough to be made en-masse and are used for big game hunting as well as a primitive form of deterrence. Bows changed little through their many countless centuries of usage, and can be found across the galaxy in a variety of designs and constructions. Because of their silence and reliability, they are used by assassins and gangers even in more advanced cultures.
Some Imperial regiments, especially those from more primitive worlds, may opt for a Bow rather then the flashlight as a Bow is quieter and less likely to have your position being found by the enemy (that, and it's much simpler to use for Feral World natives who have even less understanding of technology than most Imperials do). Of course the challenges of piercing power armor with a simple Bow is almost impossible with normal materials. Thus, it is quite common to see adamantium or diamond-tipped arrows which allow some leverage to make the Bow more compatible in war.
Types of Crossbows
Handbow
A hand bow is a smaller, one-handed version of the crossbow, effectively a pistol. It is a primitive weapon, though sometimes made with modern technology and materials and easily as powerful as a larger version.
While it can be fired with one hand it still requires a long reload time and also not when moving. As well as bows as crossbows, they are mainly used on primitive worlds, but can be found all over the galaxy in more advanced forms. The ease at which they can be broken down and concealed, as well as their silent operation, makes them a favored weapon of assassins. The Ratskin tribes of Necromunda are particularly renowned for making use of handbows and other low-tech weapons.
Purgatus Crossbow
More advanced Crossbows are also utilized by the Inquisitions Ordo Hereticus, and have become a symbol of their order. Known as the Purgatus Crossbow, it is a fusion of a Boltgun and a standard crossbow and is able to fire with more force than a Shotgun blast. However, it is its ammunition that is the true marvel; heavy wood and silver stakes inscribed with wards and runes designed to disrupt a creature's contact with the Warp, making it an excellent weapon to hunt Psykers.
It is not to be confused with the Condemner Boltgun however, as the Condemner Boltgun is a Combi-weapon whereas the Purgatus Crossbow is a modified Bolter with a Crossbow mechanism.
Stake Crossbow
A Stake Crossbow is a specialized weapon used by the Ordo Hereticus. When the Crossbow fires, it fires a silver stake engraved with sigils that destabilise a psyker's connection to the Warp. The impact of the stake against a psyker will not only cause a major wound, but it will cause his powers to go out of control, destroying the psyker in a storm of psychic energy.
The difference between this Crossbow and the Purgatus Crossbow is that one utilize Boltgun mechanics whilst the other is a more conventional Crossbow archetype. The Stake Crossbow might be attached to a bolter to form a Combi-weapon known as the Condemnor Boltgun.
Other Bow Weapons
Harpoon Gun
A Harpoon Gun is traditionally a shooting device meant to hunt down large oceanic creatures such as whales. However, this doesn't stop the denizens of the Imperium in weaponizing it. Think of the Harpoon Gun as the heavy weapon of the Bow family, even if it doesn't really use any form of a string mechanism to launch its ammunition and instead use a more spring tensile orientated mechanism.
Harpoon Guns are often used by Scalies and it has enough force and weight to puncture even power armor. However its single shot use before it needs to reload is seen as cumbersome and impractical by normal observers.
Kroot Bolt Thrower
The Kroots are also another species that is primitive enough to utilize a form of bow weaponry in the 41st Millennium. Basically a giant Ballista.
The Kroot Bolt Thrower is a primitive but effective weapon, used by the Kroot since long before they encountered the Tau Empire. Like Kroot Rifles and guns the Tau have aided their auxiliaries by using Tau technology to improve the Kroot’s weaponry.
Instead of the basic sharpened bolts the Tau provide impact fused explosive tips, making them far more dangerous. These tips are a smaller version of the warheads used in their own missile pods. The bolt thrower is fired by an ingenious hand-crank system (Similar to the Chinese repeating crossbow, the longest weapon service used in human history) which drops bolts from the magazine into position and quickly re-draws the bow string, allowing it to keep up a high rate of fire for little effort on behalf of the crew.
The Kroot Bolt Thrower often attached to the back of the Great Knarloc to enhance its battle abilities.