In the last post we looked at whether the recoil from a handgun could send a person flying. Today, staying on theme, we take another look at firearm propulsion in fantasy:
He flew up into the night sky. Unfortunately, the Ironspine was built in set-back tiers, the upper stories growing progressively narrower as you went higher. That meant that even though he Pushed himself directly up, he was soon soaring in open darkness, mists around him, the building’s side a good ten feet away.
Wax reached into his coat and removed his short-barreled shotgun from the long, sleevelike pocket inside. he turned—pointing it outward—braced it against his side, and fired.
He was light enough that the kick flung him toward the building… he slammed into the wall of the tower.
-Brandon Sanderson, The Alloy of Law
He flew up into the night sky. Unfortunately, the Ironspine was built in set-back tiers, the upper stories growing progressively narrower as you went higher. That meant that even though he Pushed himself directly up, he was soon soaring in open darkness, mists around him, the building’s side a good ten feet away.
Wax reached into his coat and removed his short-barreled shotgun from the long, sleevelike pocket inside. he turned—pointing it outward—braced it against his side, and fired.
He was light enough that the kick flung him toward the building… he slammed into the wall of the tower.
-Brandon Sanderson, The Alloy of Law
In the Mistborn Saga, for those not familiar, Allomancers are able to push and pull on metal to send themselves hurtling through the air, but Brandon Sanderson is usually pretty careful to keep these magical powers subject to the law of physics. The question today:
Can the recoil from a shotgun change the trajectory of a flying cowboy?
To answer this question, we return to the conservation of momentum. We have an Allomancer (Wax) who has just flung himself up the side of a building and is now approaching the apex of his jump. He fires a shotgun away from the building, sending the mass of the “bullet” (the shot in the shotgun) at some velocity outward in hopes of sending his own mass at some lesser velocity inward.
Referring to a shotgun recoil table, let’s assume Wax is wielding a 10 gauge with a 3.5” shell, shooting a hefty 2.25 ounces of shot outward at 1,210 feet / second. Let’s also assume (for a moment) that Wax, at his normal mass, weighs an even 200lb (3200 ounces).
This means Wax’s velocity toward the building would be 2.25/3200*1210 = 0.85 feet/second (0.6 MPH)
That’s not very fast… about 1/5 the speed of a strolling tourist. Certainly not enough to slam one into a wall.
However, looking a bit earlier in the chapter, I remember that Wax is Twinborn, meaning he has one Allomantic power (the ability to push on metal) and one Feruchemical power (the ability to change his mass). A few paragraphs before the shotgun scene, he made himself very light (to allow himself to fly higher with his Allomantic pushes).
But how light is he? Assuming he can’t change the weight of his clothes, his boots, his guns, or the iron bracers on his arm—and assuming that his body still has some mass—about the lightest he could be is 20 pounds (320 ounces).
This means Wax’s velocity toward the building would be 2.25/320*1210 = 8.5 feet/second (5.8 MPH).
That’s about the speed of a jogger running 10 minute miles… certainly not breaking the speed of sound, but fast enough to make you think twice about running into the side of a building.
Conclusion: yes, a shotgun can change the trajectory of a Twinborn Allomancer who has reached the apex of a 5-story jump and has magically made himself light enough to be significantly affected by the recoil of his weapon.
Just what you always wanted to know!
If you enjoyed this blog, check out my fantasy novels here and connect with me on social media. Thanks for reading!
This means Wax’s velocity toward the building would be 2.25/3200*1210 = 0.85 feet/second (0.6 MPH)
That’s not very fast… about 1/5 the speed of a strolling tourist. Certainly not enough to slam one into a wall.
However, looking a bit earlier in the chapter, I remember that Wax is Twinborn, meaning he has one Allomantic power (the ability to push on metal) and one Feruchemical power (the ability to change his mass). A few paragraphs before the shotgun scene, he made himself very light (to allow himself to fly higher with his Allomantic pushes).
But how light is he? Assuming he can’t change the weight of his clothes, his boots, his guns, or the iron bracers on his arm—and assuming that his body still has some mass—about the lightest he could be is 20 pounds (320 ounces).
This means Wax’s velocity toward the building would be 2.25/320*1210 = 8.5 feet/second (5.8 MPH).
That’s about the speed of a jogger running 10 minute miles… certainly not breaking the speed of sound, but fast enough to make you think twice about running into the side of a building.
Conclusion: yes, a shotgun can change the trajectory of a Twinborn Allomancer who has reached the apex of a 5-story jump and has magically made himself light enough to be significantly affected by the recoil of his weapon.
Just what you always wanted to know!
If you enjoyed this blog, check out my fantasy novels here and connect with me on social media. Thanks for reading!