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So does the thing use a portable hole for a magazine or something? Also, does the shrink spell reduce the weight too?
I think the party missed another interesting (albeit elaborate) use.
Find a large pointy rock. Shrink it down to the size of a small arrow head. Attach it to an arrow shaft such that the head will slide off the end of the shaft without too much effort (staying embedded in the target). Have the rogue launch it at the big bad, then have the barbarian or monk punch the arrow wound while wearing the ring.
I think this ring would be great for handling magic items without being affected by them. Safe way to put something sketchy looking in a sack for later study.
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.
Point is well taken, but D&D magic doesn’t take physics off the table, it violates physics within strict limits. Mundane physics still operates. As a DM a good reason I can think of for invoking physics in cases like this is that the player’s plan depends as much on physics as it does on magic, and I don’t think their cannonball trick would work. The gunpowder imparts the same momentum to the shrunken, diminished-mass cannonball as it would to a regular bullet. When the cannonball’s original size and mass are restored, it still has that much momentum - which I imagine will carry it a few feet.
Fortunately my game group includes a very smart player with a master’s degree in physics, who is very quick at computing such things. I would absolutely trust her estimate of how far the cannonball would go.
I see people make comments like this about shows, movies, etc. and I’ve never understood this line of thinking. I generally expect things to work the same as they do in real life unless it’s explicitly explained otherwise. Not sure if I’m the odd man out in thinking that way or what.
No, you’re right IMO. Just because something is different from our world doesn’t mean all logical consistency is off the table. This idea is called versimilitude.
if the ring permanently ends magical effects that enter its area of effect, that’s unusual and probably has a bunch of unexpected uses.
It it merely suppresses magical effects in its area, I guess the projectiles would briefly return to full size when in the anti-magic field, and return to small size afterwards? Doesn’t seem very effective unless you like point blank someone.
It wouldn’t work on a magical lock if you had to hold it up to it all the time
…what? With the exception of mage hand legerdemain, you’re typically very close to locks you’re picking. If it made an anti-magic field like 6" from the ring, that would be perfectly fine for picking the lock. Ring is on hand, lockpicks are in hand, magic lock is disabled.
With the exception of mage hand legerdemain, you’re typically very close to locks you’re picking
Even touching them with your hands or with the tools in your hands, I’d say. And thieves tools aren’t like several feet long or anything.
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 would hope they put the ring on a stick so the bullet-size cannonball doesn’t enter the antimagic field until it clear the barrel - otherwise it would break the barrel open. But even if they did that I don’t think the scheme would work, because when the cannonball’s original mass is restored it would have the same momentum the gunpowder gave it when it had the mass of a bullet, which wouldn’t carry a cannonball very far.
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.
That’s my take on the cannonball as well. Being diminished reduces both its size and mass, so when restored it should have the momentum gunpowder gives a bullet. I’m guessing it might go a couple feet. But this is so interesting I’m gonna ask the player in my group who has a masters in physics how far she thinks it would go.
Many of the things we take for granted as obvious these days were anything but until recently. Take bolt cutters for example. The compound lever that let’s them function so well seems like something that would have been around for centuries, but in reality wasn’t something that was widely used/understood until the 1890s when they were marketed as a wonder tool.
On the other hand, this is a game and should be fun regardless of how anachronistic it is at times. At least as long as the witch/duck proportionality is maintained. There has to be at least some realism.
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.
I was assuming that the total energy would be maintained (In this case 1350 joules) and thus the damage should be the same if weren’t spread out. It has been 20+ years since I has to do any of that math so I could be wrong about any of that. And since the only paper that was handy happened to be an envelope I guess it was technically back of the envelope math. :)
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 you can shrink and expand stuff instantly, the thing getting bigger or smaller is the least useful part of that spell. You wouldn’t even need gunpowder to launch stuff, put a shrunk cannonball against a wall, expand it, hope the wall holds and it’s the cannonball that has to accelerate to light speed to not be in the same place as the wall. Or get a giant explosion, that’s more likely.
If it dispels magic before it gets to the ring it’s going to be an issue…
Yep, and someone casting Dispel Magic on your gun would effectively ruin it, if it were loaded.
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.
If a cannonball just sprouted in a gun barrel, the gun is gone and the hands that held it probably are too. There should be so much shrapnel
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.
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).
Or, if you want to shut it down, the plan works, but since the magic effect has a range, to ball begins expanding before it makes it to the ring, taking the end of the barrel and the ring with it. If the ring is indestructible the character has to go on a search for the ring at the point of impact every time, it i expands within the ring, meaning you have a canon ball that explodes at the end of your gun with shrapnel, or you have to melt the ball down to retrieve the ring downrange.
Based on the text in the original post, I’m guessing that table ruled that the transformation took enough time for the ball to exit the gun. If not, mounting the ring out a little ways from the end of the barrel is an easy enough solution.
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.
Would the momentum stay if the mass increases?
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.
If the mass increases after the ball is already moving, then velocity should be conserved and momentum would increase with the mass. That breaks all kinds of physics rules, but this is DnD in a magical universe, there are worse violations going on.
Sorry, I should say that the momentum is conserved, but it would affect the velocity (that is, the overall kinetic energy is the same, which means velocity has to drop by an equal factor to conserve energy). It would be similar to if the extra mass were to be suddenly tethered to the bullet, which would understandably slow it down.
That being said, it’s D&D and people can rule however they want.
Why assume a conservation of momentum?
Let’s do a quick thought experiment. Let’s say you’re tossing a cannonball in your hand, and the mage shrinks it just as it leaves your hand (maximum momentum). If momentum is conserved, the cannonball would have to dramatically increase speed to conserve momentum.
Example data/assumptions:
- if tossed 1m into the air initial velocity would be 4.4m/s
- cannonball weighs 19kg
- shrunken size would be about a marble, with a mass of ~2.7g
Initial momentum of the cannonball would be 83.6 kg·m/s. If momentum is conserved, the marble would travel 30963 m/s, or Mach 90. That’s unreasonable.
So for this to make any sense, conservation of momentum shouldn’t be preserved. In other words, mass would be added with the current velocity, so it would increase momentum as it unshrinks.
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…
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