I'm creating a magic system where extremely rare humans with psychic talents could be trained to channel their powers into something similar to firing a 20 mm autocannon.

Would such large calibers used by "humans" be useful into battlefields similar to those in current age like Afghanistan, Iraq, Syria etc?

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    $\begingroup$ What are the limitations (rate of fire, total rounds that can be fired per day, range)? What is the accuracy at maximum range (autocannons come on a stable platform with sights)? What type of rounds does the magic emulate (armor piercing, high-explosive, etc.)? What are the costs and requirements for the magic soldier? How many of the autocannon-magic equipped soldiers are available? What are the costs per soldier? Without a concrete description of the limitations, it is not possible to say whether replacing an ordinary soldier with a magic solider is worthwhile. $\endgroup$ Oct 11 '21 at 0:04
  • $\begingroup$ Your autocannon-mage seems most effective with clear line-of-sight over long ranges. This suggests their enemy will quickly realize that the mages will be vulnerable to decoys, short-range ambushes, snipers and snares, attacks during limited-visibility (night, fog), and attacks when they are asleep. Plus vulnerability to classic dramatic ploys like politics, poisoning, bribery, and relationship betrayal. A smart enemy commander will --as always-- adapt. Firepower is only one element of success. $\endgroup$
    – user535733
    Oct 11 '21 at 1:18
  • $\begingroup$ As asked, this appears to violate the help center rules. You've asked an open-ended question that's inviting opinions, rather than addressing the help center rule that questions must be specific and answerable. When wouldn't a 20mm cannon be useful? Who cares how it manifests (psychics... magnetics... chemical propellant... slingshots...), of course they'd be useful. So, what problem with the rules of your world are you having trouble with? How to balance the psychic powers of your "magic users" vs. the other combat tech? $\endgroup$ Oct 11 '21 at 1:20
  • $\begingroup$ @GrumpyYoungMan Same as autocanon, 1000 rounds, same as autocanon. There are no special costs beside the cost of the weapon about 500,000$. Very few soldiers are available something rare as most elite delta force / devgru teams. $\endgroup$
    – 0331
    Oct 11 '21 at 9:14

It depends on how long they can sustain this. If the magic is based only on concentration, and they can therefore go on for as long as they want, it'd be fantastic, as it wouldn't require any ammunition.

A big advantage I'd see in a war with magic users basically being able to mimic the effects of a machine gun or larger weapon, is that it is far, far more easy to transport. Being able to field a large number of these magic users, could be used for interesting blitzkrieg (lightning war) and guerilla warfare tactics, and thus the army with the bigger stick, so to speak, would have a big advantage in mobility. I imagine something like how in Brandon Sanderson's Stormlight Archive, wars are fought just to get the legendary shardblades.

So yes, I'd say that it would be effective in modern combat. Especially in rough terrain, not having to carry a gun with you would be very convenient.


Yes, light machine guns uses 5.56mm calibre bullets, while general purpose machine guns uses 7.62mm. Anything above, such us 50 cal is mounted on a vehicle i.e. not something carried on foot. With 20mm and unlimited ammo you have an infantry fighting vehicle that could enter into compounds. Just for comparison imagine being hit by rightmost bullet. The word overkill is an understatement.




Lovely anecdote about the power of 50 cal round.

During Desert Shield, someone accidentally discharged a .50 BMG. It went front to back thru a Chevy Suburban, thru the engine block took the driver’s set out the back window,then went downrange. A mile down range a Marine was on a sand berm on patrol and that round hit him in the shoulder and took his left arm off. No one knows were it ended up after that. I was one of that marine’s surgeons. link

In both pics the small one is .50BMG link enter image description here enter image description here

Image credit to cartridge company blog


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