I recently played the game Mary Skelter - Nightmares, in which the protagonist after some time acquires a weapon that is called a Mary Gun - a device that shoots his own blood.
I'll change the properties this gun has in the game a bit:
- A Blood Gun is supposed to be a gun-like device strapped to the hand/forearm of the wielder.
- A syringe that is part of the weapon design is able to draw out blood from the wielder.
- When pressing the trigger the gun shoots the blood of the wielder at the enemy.
- The weapon can store a certain amount of blood so that there is enough blood readily available when needed.
- The wielders blood is an effective way to deal damage to enemies that are hit by it - assume the blood has some magical property that damages magical creatures that get into contact with it somehow. This magical property can be ignored when making assumptions related to the blood. The gun is merely used to deliver the blood reliably over a distance of at least a few feet when needed.
Such a Blood Gun poses quite a few problems:
- How many times can the gun be fired in a row?
The answer to this problem is comprised of two separate problems:- How much blood can I drain from an average adult German male (~80kg at ~180cm) before my protagonist falls unconscious in a stress situation?
Unconsciousness in battle would mean the end of my protagonist. - How much blood do I need to shoot for each shot?
Depending on the design there may be a minimum amount of blood, for example to build up pressure. The gun should be able to fire the blood at a distance of at least a few feet.
- How much blood can I drain from an average adult German male (~80kg at ~180cm) before my protagonist falls unconscious in a stress situation?
- How far can I shoot the blood in its liquid form?
The farther, the better. - How fast can I drain the blood without my protagonist suffering any medical difficulties?
Drawing a huge amount of blood in a matter of seconds may introduce problems for my protagonist, but the faster I can draw the blood, the better. - How can I make sure that the blood doesn't clump inside the gun?
Depending on the design the blood doesn't need to be fired directly after being drawn out of the wielders body, but could instead be kept inside the gun. This could for example be used to build up pressure and to already have a "bullet" ready when it's needed, which requires anticoagulants being stored in sufficient quantity and applied to the important parts of the gun without affecting the wielder. Otherwise my gun might not work the way I want it to work in a critical situation, for example because the blood won't be able to pass through the exit. - How much weight is acceptable as a sort of gun that is wielded in one hand and therefore limits the amount of parts and storage of the gun?
A design that requires the protagonist to carry multiple kilograms of equipment attached to their hand would be problematic when trying to escape danger or when trying to quickly target an enemy. - How can I make sure that my wielder will not die from blood loss the moment something damages the gun?
If something hits the gun and suddenly the syringe rips open my protagonists' arteries he will surely die without any help.
All of these problems lead me to the question:
How can I build a Blood Gun with present day technology?
This question is purely about the technological considerations that I need to account for in such a weapon.
The fact that shooting your own blood doesn't look like an intelligent way to combat enemies can be ignored. Other solutions, such as preparing "blood bullets" in advance and simply having a couple cartridges with you are outside the scope of this question.
For all cases where you have to make assumptions about technology you can assume real world technology. For all assumptions about the wielder and his blood you can assume an average adult European male.
Answers should take the problems outlined above into considerations. The more problems you discover that I couldn't find the better.
This question is different from Building a Syringe Gun, which basically asks about a tranquilizer gun, because I don't want to simply fire liquids in cartridges or containers of any kind - I want to shoot blood in its liquid form, like a water pistol, with the blood taken more or less directly from the wielder of the gun when pulling the trigger.