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I love how everyone is discussing the physics of a cannonball gun DIY setup in a game where magic can instantly teleport people or turn a person into a huge dragon.
I’m not complaining, I just find it amusing.
So that is engineering. Is this character an engineer with knowledge of magic, physics and mechanics?
It’s fine and easy for a player to think in term of game mechanics. But the actual process is not so goofy. And the character is not the player. The dice decide after that.
I dunno sounds like the only even vaguely engineering part is glueing a ring to the end of a pistol? If that’s considered out of the box clever enough to require a check I can only assume D&D takes place in the systemic lead poisoning dimension.
I think the engineering part kicks in once the cannonball leaves the ring, or maybe around the mass of the shrunken ball. If the cannon ball retains it’s mass in it’s shrunken size does the gun have enough power to move it? If it does, then the gun is a ship cannon already, just a convenient size. If it doesn’t and can only shoot because the balls are as easy to fire as regular shot, then as soon as the ball exits the ring it is a cannonball being moved with the force of a small shot and likely drops to the ground an inch or so past the muzzle.
I imagine that the momentum would be conserved. So if the rifle normally shot a 30 gram ball at 300 meters per second, it would shoot a 5 kilogram ball at around 23 meters per second.
- The larger size and lower speed of the cannon ball would likely reduce the range.
- The larger size of the projectile would spread out the impact causing reduced damage.
- The ballistics would be significantly different making it far harder to hit with.
This is how I would do it in my game:
- Reduce the damage from 1d12 to 1d10
- Change piercing type to bludgeoning
- Reduce range from 40/120 to something like 20/60
- Add knockback of 5 ft to medium targets or 10 for small
The really neat thing would be shooting non standard rounds that wouldn’t be possible from a musket like incendiary or smoke rounds.
I think damage reduction would be even more than that. The damage a projectile does to a target is directly related to its kinetic energy which is calculated as e = ½mv². So when you increase mass but reduce velocity you also reduce the damage by the square of the difference in velocity (I think). As long as the damage just relies on the physics of the projectile and not magic, that is.
Wouldn’t it dispell the magic before it got to the ring? So your gun just exploded and your ring is now somewhere downrange?
You’d have to mount it on a wire a bit past the end of the barrel, or custom create a barrel that expands toward the end. Depends on whether dispelling the magic is an instant transformation, or if it “grows” at some rate.
If it dispels magic before it gets to the ring it’s going to be an issue…
Yeah, if its range is enough to dispel a lock, then it must be at least an inch. So the cannon ball grows while an inch down the barrel.
Meme is still correct though as that’s my face while calculating what to change so they don’t TPK or something when they try it on the next encounter…
Rogue fires gun. Cannonball grows and shatters the gun. Gun pieces fall to floor in front of rogue. If you look, the ring is still in the wreckage, and still usable. Enemy spends a turn just looking at the rogue in amusement. Turn after goes as usual.
They would have gone all in on this strat and left themselves open for shenanigans.
Or decided to test it inside or something.
If it is a muzzle loader, no you don’t.
I suppose you’d have to remove the ring while loading in that case?
Good way to lose the ring.
Would the momentum stay if the mass increases?
Momentum could still be conserved if the velocity is unchanged, but it would mean there’s now a lot of kickback once it gets big…
Lol the ball just falls out the end like a defective Acme gun
As another poster mentioned, this is likely the reason this isn’t already done in the fantasy setting. Either the mass is the same (in which case your flintlock isn’t going to launch it terribly far) or the mass changes and it would reduce momentum.
That being said, it’s still a useful way to transport cannonballs, and could still be quite useful. Just not quite a “free” Catapult spell on demand.
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Because I hate fun, I assume that the people in a fantasy world aren’t all fools so if there’s an application of magic that seems obvious but isn’t already happening in the setting, there’s a good reason for that.
There’s also the rule of “if you can do it, so can NPCs”. Even if your character has thought of something no one in the universe has thought of before, word will get around.
I have it as: “cool idea, i’ll let you get away with it once. Start abusing it and all the NPCs start using it.” works pretty good.
This is a good take, but it partly depends on the setting. Specifically, if these magic artifacts are fairly rare and valuable (even something meager like this ring), it’s entirely possible that people haven’t explored that kind of application of magic. It could also be viable if there are very few inventors/scholars in the setting.
In any case, the conservation of mass thing another commenter mentioned would make this less viable, so you’re right on the money. That being said, laws of physics can be bent for rule-of-cool if that’s your table. Personally, if I were DMing it, I’d probably try to find a way to balance between realism and making their research process hilarious and/or dangerous, with the end result being them producing something useful but not gamebreaking (e.g., you can carry and deploy the cannonballs, but the gun doesn’t really fire them, but in combination with a method of flight, could still be awesome–or they apply this method with a large boulder and have that to work with instead).
Sounds as if you play as most unimaginative character that does everything in a dullest way possible. What’s the point of playing tabletop then? I mean half of the fun of tabletop rpgs is exploring the possibilities and creativity (for me).
The vibe I like is “gritty action movie”. Some people prefer something zanier.
