Understandably, a DM doesn't like it when we come up with solutions to something he thought was a clever twist. But now, I think my DM is ignoring the written game rules to obviate the solution.
So, very cool, we have firearms in his homebrewed campaign setting, and as an Artificer, I can use the Hunting Rifle we took off an opponent's corpse. DM's twist to not have that become a game-breaker, is that ammunition is, of course, limited for such an "exotic" weapon, and I can't make more key ingredient, gunpowder (discovering the formula for gunpowder is part of my personal quest in this). After the grace period of a few days of game time and a few combats, now that I've looted 100 pieces of ammo from our last foe, he will keep track of ammo spent, so that conserving ammo is a factor in encounters. Fair enough.
Except, I have the Repeating Shot Infusion - "If the weapon lacks ammunition, it produces its own, automatically creating one piece of magic ammunition when the wielder makes a ranged attack with it." So I would say that means I will never run out.
As part of leveling up after the last session, I emailed him about this. His reply "... So, agree to all except the repeating shot replicating the ammo. The formula for gunpowder has been lost, so you do not know how to replicate it. That is why it is so important for you to the quest to rediscover it."
I explained that _I_ am not replicating or making gunpowder, I'm not actually doing anything. The _gun_ is making magic bullets as part of the infusion. Nothing that requires any particular knowledge, it's magic.
Still no, that I am replicating and need to know the formula myself. If I was saying a spell "Create Gunpowder!" I would agree that it might require me to have an idea in my head of what ingredients I am pulling from the ether, but I am not doing that.
If it was a bow, making magic arrows, it wouldn't require me to have studied to be a fletcher...
I know that this takes some urgency out of the quest he gave me, to recover the secret of gunpowder, but it seems silly to deny that the infusion does what it does.
No you don't need knowledge of how to make ammunition and it has nothing to do with gunpowder, Repeating Shot produces its own ammunition, automatically creating one piece of magic ammunition when you make a ranged attack with it. It's a houserule of its own.
I'm with the GM. A quest to find the recipe is a cool idea, and fits with the tropes of the genre. High fantasy is filled with quests to uncover forgotten knowledge (previously unknown spells, knowledge of how to create magic items, new martial arts, scrolls of arcane knowledge, and so on).
You don't get to bypass a quest by pointing at a line in a rulebook. If you want to do the quest, do it. If you don't want to do it, that's fine too, but you don't get the rewards.
I'm with the GM. A quest to find the recipe is a cool idea, and fits with the tropes of the genre. High fantasy is filled with quests to uncover forgotten knowledge (previously unknown spells, knowledge of how to create magic items, new martial arts, scrolls of arcane knowledge, and so on).
You don't get to bypass a quest by pointing at a line in a rulebook. If you want to do the quest, do it. If you don't want to do it, that's fine too, but you don't get the rewards.
So I get this in its entirety but that is not how the ability works.
The ability in question just says it make this ammo, doesn't care what ammo it is it make the ammo for that weapon. Its also not about reading a line a rule book to bypass something its class ability given to that class.
Repeating Shot
Item: A simple or martial weapon with the ammunition property (requires attunement)
This magic weapon grants a +1 bonus to attack and damage rolls made with it when it’s used to make a ranged attack, and it ignores the loading property if it has it.
If you load no ammunition in the weapon, it produces its own, automatically creating one piece of magic ammunition when you make a ranged attack with it. The ammunition created by the weapon vanishes the instant after it hits or misses a target.
As a Dm you want to work with your players and work the story into the mix. Something like this could have been better off saying this weapon is so exotic that you don't know how to use it and cannot place the infusion on it till you do. Or that the weapon needs to be fixed and you incorporate that into the story and have them say find the schematics with the gunpowder formula. But to say you don't know how to make gun powder so that ability doesn't work is silly, by that logic wizards cant cast half the spells cause we wouldn't understand half the concepts that cause the spells to happen. You could say give them a bonus for using real bullets? Say they do more damage?
Either way IMO this could have been a better story beat instead of a rules issue. RAW no you don't need ammo or the know how to create the ammo. Rules as your DM plays it make sure you learn alchemy tools......
It doesn’t matter what the ability says. Rule number 1 is that the DM can use, modify, ignore or create new rules for their games as they see fit. If the DM doesn’t like that part of the ability then they are absolutely at liberty to say no.
Well, I guess I just wanted to be sure that my argument was sound. It is the DM's world, and his plans, so I can only ask.
I'd rather he had just said, you know, this really messes with the flow, not claim that I was reading incorrectly.
The DM could also have said that the weapon had some sort of enchantment already on it that fortified its reliability and was thus ineligible for the infusion. That would achieve the same effect, but would add a bit of lore to the world that could lead to new adventures later. I think that would have been much more interesting than adding a new restriction to one of the players' class features.
Well, I guess I just wanted to be sure that my argument was sound. It is the DM's world, and his plans, so I can only ask.
I'd rather he had just said, you know, this really messes with the flow, not claim that I was reading incorrectly.
The DM could also have said that the weapon had some sort of enchantment already on it that fortified its reliability and was thus ineligible for the infusion. That would achieve the same effect, but would add a bit of lore to the world that could lead to new adventures later. I think that would have been much more interesting than adding a new restriction to one of the players' class features.
That would make it a magic item then, no? It's pretty understandable why the DM doesn't want a player to have an absurdly strong ranged weapon - stronger than any melee weapon, mind you - on hand at all times with no real cost, that also cuts through the very common nonmagical physical resistance.
While the DM can do as he/she please, it's generally better to tell houserules in advance especially when it involve the player characters abilities resulting in not being able to use class features it normally should. Being told on the fly you must research before you can use your Artificer's infusion is not ideal. Especially if other PCs get to use their new features without research or training first.
Well, I guess I just wanted to be sure that my argument was sound. It is the DM's world, and his plans, so I can only ask.
I'd rather he had just said, you know, this really messes with the flow, not claim that I was reading incorrectly.
You're not reading incorrectly and your argument is sound. This thread is in the Rules & Game Mechanics everyone here can tell your reading is the correct one. Conciously or not the DM views this Artificer's Infusion differently that RAW, either due to misinterpretation or houseruling.
Well, I guess I just wanted to be sure that my argument was sound. It is the DM's world, and his plans, so I can only ask.
I'd rather he had just said, you know, this really messes with the flow, not claim that I was reading incorrectly.
The DM could also have said that the weapon had some sort of enchantment already on it that fortified its reliability and was thus ineligible for the infusion. That would achieve the same effect, but would add a bit of lore to the world that could lead to new adventures later. I think that would have been much more interesting than adding a new restriction to one of the players' class features.
That would make it a magic item then, no? It's pretty understandable why the DM doesn't want a player to have an absurdly strong ranged weapon - stronger than any melee weapon, mind you - on hand at all times with no real cost, that also cuts through the very common nonmagical physical resistance.
Keep in mind, Moontouched weapons are "Common" magic items.
Also, there's an argument that there's a difference between magical augmentation to damage, and magical augmentation to damage (ex: if the halfling is wearing magic +1 plate armor, and the Barbarian picks up the Halfling as an improvised weapon, that magic armor won't count as a magic +1 weapon because that's not what the enchantment does.)
Besides, bypassing resistance to non-magical damage is a small price to pay for a DM who doesn't want a player to have infinite ammo. Everyone wins.
RAW, your DM is wrong. however, if part of your quest is finding gunpowder, then it would make sense for him to want you to keep that quest. Talk to your DM about whether or not you want to continue that plotline; if not, using the RAW lets you continue using the gun. However, if you find the plotline interesting and want to continue, your DMs ruling would make sense as an in character reason to continue, even if it doesn't fit RAW. Your DM likely knows this is now RAW. He simply wants to give you a reason to continue the quest that makes sense, should you seek to do so.
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I write homebrew and don't publish it. (evil, I know)
I think if nothing else you should go ahead and embrace this as a homebrew opportunity. If your DM is going to homebrew that an Infusion just doesn't work as-written because it creates a problem for the story, you should be able to modify the infusion to compensate. You could, theoretically, just swap it for the Enhanced Weapon infusion, since that eventually becomes a +2 weapon, giving you at least something beyond what Repeating Shot offers. But one of the other functions of Repeating Shot is that it allows you to ignore the Loading Property, giving you more of an automatic weapon. Maybe if you're dropping the ability to create your own ammo you could swap it for another feature... nothing too wild, maybe just add a feature that attacking at long range doesn't impose disadvantage on your attacks... so you still can't produce your own ammo, but the infusion still makes the gun more useful than it would otherwise be.
Item: A simple or martial weapon with the ammunition property (requires attunement)
This magic weapon grants a +1 bonus to attack and damage rolls made with it when it’s used to make a ranged attack, and it ignores the loading property if it has it.
Could the DM be interpreting this as either the artificer did not make the weapon and thus its not available as a reloadable magic weapon for him or its simply not a magic weapon at all.
Does an artificer make ANY crossbow he picks up a repeating crossbow(thus making it magic) or does he have to create the crossbow from scratch like he does with other magic items.
would repeating shot still fire a magic bolt/bullet/thing from the given device if you...
attempted to fire a crossbow with no bow string?
attempted to fire a crossbow with no bow, only the grooved center stock?
attempted to fire a rifle with no gunpowder load?
the ability description doesn't give a caveat to propellant so 'yes, because magic' seems to be RAI; however, it's not implausible for the DM to rule that the magic isn't happy unless you have your gunpowder license first. no different than running up against a door with an 'unpickable lock' and a key quest. well, except that the DM has allowed you an arbitrary number of demonstration shots to test it out. heck, you might not even run out of those before you solve the quest. better to enjoy what you have (and definitely hope the DM doesn't think up misfire rates).
Have you guys never given a plot item "Resistance to Divination Magic" so it can't just be Identified?
Sure, give some details when the identify is spell is cast, give hints, ect. But you don't have to give away all the mystery of the plot device because "RAW it says identify tells you all".
Granted you can't make every door immune to "knock" spell, but for the sake of the story sometimes there is a door that doesn't work on. That's not a DM nerffing the wizard. And it is def a fine line to ride and sometimes you have to let the knock / identity / whatever spell instantly solve puzzle to reward those char choices, but a DM gets to have a plot device every now and then.
I'm with the DM here, they've given you a story element and asked if you like to participate in it. Pass on it and skip the item, or delve head first into the quest and story element to figure out how this thing works, so you can apply your enchantments to it. If that isn't your concept of fun, then I guess you might be at the wrong table? some like to play DnD like a vid game. And there nothing wrong with that. Some want to make a story.
(but yes, as you've been told by everyone already RAW you are right and the DM is trying to keep things interesting. But you already knew that. so...)
RAW, the infusion should produce ammunition for any weapon with the ammunition property. The ammunition only appears when you make a ranged attack and disappears as soon as it hits or misses. Whatever the infusion creates is magic. The infusion may not even be creating gunpowder - just something that can be fired from the gun as if it had gunpowder in it. The ammunition can neither be harvested for gunpowder nor could the formula for gunpowder be found by examining the ammunition produced.
As a result, the only impact in the campaign of the infusion is that it gets rid of the whole ammunition tracking mini-game. However, as an artificer, you can be using your repeating shot infusion on a heavy crossbow and doing d10 damage with each attack. Admittedly, a hunting rifle in the DMG does 2d10 for comparison so it is clearly better but if the DM wants to limit ammo, the artificer can just keep both the hunting rifle and the heavy crossbow and then refuse to pull out the hunting rifle except when they really want the extra damage.
The end result is the special weapon, that the DM wants to be so cool and wants to limit its use via an ammo tracking mini-game, just ends up not being used most of the time.
Also, keep in mind that the heavy crossbow is a lot quieter than a hunting rifle. The rifle could attract attention for miles (or a Balrog deep below the surface :) ), the heavy crossbow not at all.
----
However, it is perfectly ok for a DM to houserule that the infusion doesn't work with firearms or ask that the artificer know something about making the items that they are infusing. It would be nice if they let you know in advance but sometimes the DM hasn't thought that far or doesn't know all the abilities of all the characters. So, in this case, the OP should just go along with it and perhaps just stick to using their heavy crossbow. If the DM sees the weapon going unused due to ammo tracking limitations they might change their mind.
Last comment, in my opinion, resource tracking to limit the use of specific abilities (like ammo for a weapon or a limited supply of a consumable spell component) are usually not a fun way to manage a plot element from a player perspective. It usually just isn't much fun. (Most folks don't seem to want to track water/food/ammunition etc except in the broadest terms - ie they have some or they do not).
Have you guys never given a plot item "Resistance to Divination Magic" so it can't just be Identified?
Sure, give some details when the identify is spell is cast, give hints, ect. But you don't have to give away all the mystery of the plot device because "RAW it says identify tells you all".
Granted you can't make every door immune to "knock" spell, but for the sake of the story sometimes there is a door that doesn't work on. That's not a DM nerffing the wizard. And it is def a fine line to ride and sometimes you have to let the knock / identity / whatever spell instantly solve puzzle to reward those char choices, but a DM gets to have a plot device every now and then.
I'm with the DM here, they've given you a story element and asked if you like to participate in it. Pass on it and skip the item, or delve head first into the quest and story element to figure out how this thing works, so you can apply your enchantments to it. If that isn't your concept of fun, then I guess you might be at the wrong table? some like to play DnD like a vid game. And there nothing wrong with that. Some want to make a story.
(but yes, as you've been told by everyone already RAW you are right and the DM is trying to keep things interesting. But you already knew that. so...)
I disagree with your premise that it's a "good" idea for the DM to decide that spells sometimes don't work when they RAW would have. Those spells that identify objects or open doors are so niche already without having them not work in exactly the situations the players took them for. Artifacts already defy Identify. If a lower-rarity magic item had a charm on it to resist Identification, then that charm should conceivably be suppressible with a Dispel Magic, which would then allow the full range of spells and enchantments affecting the item to be identified with the Identify spell. This makes it a bit more of a puzzle to get the information, but the players have the resources to overcome it, which is much more satisfying than having everything not work because the story isn't ready for it. No one likes to run into invisible walls in what's supposed to be an open world.
Don't make any doors immune to Knock. A door might have a glyph that counterspells knock, but that glyph should be dispellable, the lock pickable, the door breakable, etc. Each of these may be challenging, but shouldn't be impossible. D&D is not a video game. In videogames, players accept that there are doors that are inexplicably unopenable until the story calls for it, because there are finite possibilities for what programmers can put into the games, and many of these limitations are not applicable to tabletop RPGs.
The players have versatile tool sets, and sometimes the DM's role is to "yes, and" even if it makes something easier for the players than the DM initially intended. The thing to remember is that these spells are limited resources the players have, and if they are willing to use them to identify objects and open doors, they have that much less to work with when they get into a battle later. These spells also take up spells-known or spells-prepared slots, so it burns twice as hard when a player is ex-post-facto nerfed by the DM at a point when the player was expecting to shine. If they run into rooms full of plant-monsters after the wizard all of his L2+ spell slots on disabling traps and opening doors, that will be a much harder fight than it would have been if the DM had saved those slots for Dragon's Breath and/or Fireball. They had it easer earlier, but at the expense of them facing greater challenge later. It's the DM's job to balance it out.
DMs can also put more locks on doors. Maybe a particularly important door has a half-dozen locking mechanisms on it, which makes it worth the players' time to find the keys or clues of how to open it, rather than brute-forcing it with magic. But if this is done, that should be observable, before the players start expending resources against it.
That's the same thing. Your artificially countering knock so it doesn't open the door. Put 12 locks on it, glphy to dispell... yeah you just made a knock proof door.
Your just arguing to flavor it better. And you did flavor it better.
We can just link to the threads on quantum ogres at this point. Yes a fully flushed out world that is always ready for players to where they want, and truly open is best. but sometimes the appearance of it is good enough and we don't all have the ability to have every path flushed out and ready to go. Sometimes that door is a hook for the next campaign.
Edit: To be clear the DM in this example is going to allow the player the infusion, they can absolutely use it in all the normal ways. This homebrew item meant to be OP and provide interesting choices and quest/story content just isn't going to interact with it. How ever you wanna flavor that "sure you materialize the lead shot, but there is no powder" OR "It's magical so you can't add an infusion to it" isn't itself a horrible violation of player agency/choice/nerf bat whatever.
I don’t have artificers, I do have guns, and I would have allowed it.
I have something akin to an artificer (a runewright), so that wouldn’t be an issue, and since my firearms are generally available (except, of course, the special ones, that it is a death sentence to have, blah blah) this would be a very high demand thing, lol.
that said, I have to side with the DM because his setting.
I dislike the ruling, though.
Rollback Post to RevisionRollBack
Only a DM since 1980 (2000+ Sessions) / PhD, MS, MA
Understandably, a DM doesn't like it when we come up with solutions to something he thought was a clever twist. But now, I think my DM is ignoring the written game rules to obviate the solution.
So, very cool, we have firearms in his homebrewed campaign setting, and as an Artificer, I can use the Hunting Rifle we took off an opponent's corpse. DM's twist to not have that become a game-breaker, is that ammunition is, of course, limited for such an "exotic" weapon, and I can't make more key ingredient, gunpowder (discovering the formula for gunpowder is part of my personal quest in this). After the grace period of a few days of game time and a few combats, now that I've looted 100 pieces of ammo from our last foe, he will keep track of ammo spent, so that conserving ammo is a factor in encounters. Fair enough.
Except, I have the Repeating Shot Infusion - "If the weapon lacks ammunition, it produces its own, automatically creating one piece of magic ammunition when the wielder makes a ranged attack with it." So I would say that means I will never run out.
As part of leveling up after the last session, I emailed him about this. His reply "... So, agree to all except the repeating shot replicating the ammo. The formula for gunpowder has been lost, so you do not know how to replicate it. That is why it is so important for you to the quest to rediscover it."
I explained that _I_ am not replicating or making gunpowder, I'm not actually doing anything. The _gun_ is making magic bullets as part of the infusion. Nothing that requires any particular knowledge, it's magic.
Still no, that I am replicating and need to know the formula myself. If I was saying a spell "Create Gunpowder!" I would agree that it might require me to have an idea in my head of what ingredients I am pulling from the ether, but I am not doing that.
If it was a bow, making magic arrows, it wouldn't require me to have studied to be a fletcher...
I know that this takes some urgency out of the quest he gave me, to recover the secret of gunpowder, but it seems silly to deny that the infusion does what it does.
Thoughts?
No you don't need knowledge of how to make ammunition and it has nothing to do with gunpowder, Repeating Shot produces its own ammunition, automatically creating one piece of magic ammunition when you make a ranged attack with it. It's a houserule of its own.
So I get this in its entirety but that is not how the ability works.
The ability in question just says it make this ammo, doesn't care what ammo it is it make the ammo for that weapon. Its also not about reading a line a rule book to bypass something its class ability given to that class.
Repeating Shot
Item: A simple or martial weapon with the ammunition property (requires attunement)
This magic weapon grants a +1 bonus to attack and damage rolls made with it when it’s used to make a ranged attack, and it ignores the loading property if it has it.
If you load no ammunition in the weapon, it produces its own, automatically creating one piece of magic ammunition when you make a ranged attack with it. The ammunition created by the weapon vanishes the instant after it hits or misses a target.
As a Dm you want to work with your players and work the story into the mix. Something like this could have been better off saying this weapon is so exotic that you don't know how to use it and cannot place the infusion on it till you do. Or that the weapon needs to be fixed and you incorporate that into the story and have them say find the schematics with the gunpowder formula. But to say you don't know how to make gun powder so that ability doesn't work is silly, by that logic wizards cant cast half the spells cause we wouldn't understand half the concepts that cause the spells to happen. You could say give them a bonus for using real bullets? Say they do more damage?
Either way IMO this could have been a better story beat instead of a rules issue. RAW no you don't need ammo or the know how to create the ammo. Rules as your DM plays it make sure you learn alchemy tools......
It doesn’t matter what the ability says. Rule number 1 is that the DM can use, modify, ignore or create new rules for their games as they see fit. If the DM doesn’t like that part of the ability then they are absolutely at liberty to say no.
Well, I guess I just wanted to be sure that my argument was sound. It is the DM's world, and his plans, so I can only ask.
I'd rather he had just said, you know, this really messes with the flow, not claim that I was reading incorrectly.
The DM could also have said that the weapon had some sort of enchantment already on it that fortified its reliability and was thus ineligible for the infusion. That would achieve the same effect, but would add a bit of lore to the world that could lead to new adventures later. I think that would have been much more interesting than adding a new restriction to one of the players' class features.
That would make it a magic item then, no? It's pretty understandable why the DM doesn't want a player to have an absurdly strong ranged weapon - stronger than any melee weapon, mind you - on hand at all times with no real cost, that also cuts through the very common nonmagical physical resistance.
While the DM can do as he/she please, it's generally better to tell houserules in advance especially when it involve the player characters abilities resulting in not being able to use class features it normally should. Being told on the fly you must research before you can use your Artificer's infusion is not ideal. Especially if other PCs get to use their new features without research or training first.
You're not reading incorrectly and your argument is sound. This thread is in the Rules & Game Mechanics everyone here can tell your reading is the correct one. Conciously or not the DM views this Artificer's Infusion differently that RAW, either due to misinterpretation or houseruling.
Keep in mind, Moontouched weapons are "Common" magic items.
Also, there's an argument that there's a difference between magical augmentation to damage, and magical augmentation to damage (ex: if the halfling is wearing magic +1 plate armor, and the Barbarian picks up the Halfling as an improvised weapon, that magic armor won't count as a magic +1 weapon because that's not what the enchantment does.)
Besides, bypassing resistance to non-magical damage is a small price to pay for a DM who doesn't want a player to have infinite ammo. Everyone wins.
RAW, your DM is wrong. however, if part of your quest is finding gunpowder, then it would make sense for him to want you to keep that quest. Talk to your DM about whether or not you want to continue that plotline; if not, using the RAW lets you continue using the gun. However, if you find the plotline interesting and want to continue, your DMs ruling would make sense as an in character reason to continue, even if it doesn't fit RAW. Your DM likely knows this is now RAW. He simply wants to give you a reason to continue the quest that makes sense, should you seek to do so.
I write homebrew and don't publish it. (evil, I know)
I think if nothing else you should go ahead and embrace this as a homebrew opportunity. If your DM is going to homebrew that an Infusion just doesn't work as-written because it creates a problem for the story, you should be able to modify the infusion to compensate. You could, theoretically, just swap it for the Enhanced Weapon infusion, since that eventually becomes a +2 weapon, giving you at least something beyond what Repeating Shot offers. But one of the other functions of Repeating Shot is that it allows you to ignore the Loading Property, giving you more of an automatic weapon. Maybe if you're dropping the ability to create your own ammo you could swap it for another feature... nothing too wild, maybe just add a feature that attacking at long range doesn't impose disadvantage on your attacks... so you still can't produce your own ammo, but the infusion still makes the gun more useful than it would otherwise be.
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Repeating Shot
Item: A simple or martial weapon with the ammunition property (requires attunement)
This magic weapon grants a +1 bonus to attack and damage rolls made with it when it’s used to make a ranged attack, and it ignores the loading property if it has it.
Could the DM be interpreting this as either the artificer did not make the weapon and thus its not available as a reloadable magic weapon for him or its simply not a magic weapon at all.
Does an artificer make ANY crossbow he picks up a repeating crossbow(thus making it magic) or does he have to create the crossbow from scratch like he does with other magic items.
would repeating shot still fire a magic bolt/bullet/thing from the given device if you...
the ability description doesn't give a caveat to propellant so 'yes, because magic' seems to be RAI; however, it's not implausible for the DM to rule that the magic isn't happy unless you have your gunpowder license first. no different than running up against a door with an 'unpickable lock' and a key quest. well, except that the DM has allowed you an arbitrary number of demonstration shots to test it out. heck, you might not even run out of those before you solve the quest. better to enjoy what you have (and definitely hope the DM doesn't think up misfire rates).
Have you guys never given a plot item "Resistance to Divination Magic" so it can't just be Identified?
Sure, give some details when the identify is spell is cast, give hints, ect. But you don't have to give away all the mystery of the plot device because "RAW it says identify tells you all".
Granted you can't make every door immune to "knock" spell, but for the sake of the story sometimes there is a door that doesn't work on. That's not a DM nerffing the wizard. And it is def a fine line to ride and sometimes you have to let the knock / identity / whatever spell instantly solve puzzle to reward those char choices, but a DM gets to have a plot device every now and then.
I'm with the DM here, they've given you a story element and asked if you like to participate in it. Pass on it and skip the item, or delve head first into the quest and story element to figure out how this thing works, so you can apply your enchantments to it. If that isn't your concept of fun, then I guess you might be at the wrong table? some like to play DnD like a vid game. And there nothing wrong with that. Some want to make a story.
(but yes, as you've been told by everyone already RAW you are right and the DM is trying to keep things interesting. But you already knew that. so...)
Just to chime in ...
RAW, the infusion should produce ammunition for any weapon with the ammunition property. The ammunition only appears when you make a ranged attack and disappears as soon as it hits or misses. Whatever the infusion creates is magic. The infusion may not even be creating gunpowder - just something that can be fired from the gun as if it had gunpowder in it. The ammunition can neither be harvested for gunpowder nor could the formula for gunpowder be found by examining the ammunition produced.
As a result, the only impact in the campaign of the infusion is that it gets rid of the whole ammunition tracking mini-game. However, as an artificer, you can be using your repeating shot infusion on a heavy crossbow and doing d10 damage with each attack. Admittedly, a hunting rifle in the DMG does 2d10 for comparison so it is clearly better but if the DM wants to limit ammo, the artificer can just keep both the hunting rifle and the heavy crossbow and then refuse to pull out the hunting rifle except when they really want the extra damage.
The end result is the special weapon, that the DM wants to be so cool and wants to limit its use via an ammo tracking mini-game, just ends up not being used most of the time.
Also, keep in mind that the heavy crossbow is a lot quieter than a hunting rifle. The rifle could attract attention for miles (or a Balrog deep below the surface :) ), the heavy crossbow not at all.
----
However, it is perfectly ok for a DM to houserule that the infusion doesn't work with firearms or ask that the artificer know something about making the items that they are infusing. It would be nice if they let you know in advance but sometimes the DM hasn't thought that far or doesn't know all the abilities of all the characters. So, in this case, the OP should just go along with it and perhaps just stick to using their heavy crossbow. If the DM sees the weapon going unused due to ammo tracking limitations they might change their mind.
Last comment, in my opinion, resource tracking to limit the use of specific abilities (like ammo for a weapon or a limited supply of a consumable spell component) are usually not a fun way to manage a plot element from a player perspective. It usually just isn't much fun. (Most folks don't seem to want to track water/food/ammunition etc except in the broadest terms - ie they have some or they do not).
I disagree with your premise that it's a "good" idea for the DM to decide that spells sometimes don't work when they RAW would have. Those spells that identify objects or open doors are so niche already without having them not work in exactly the situations the players took them for. Artifacts already defy Identify. If a lower-rarity magic item had a charm on it to resist Identification, then that charm should conceivably be suppressible with a Dispel Magic, which would then allow the full range of spells and enchantments affecting the item to be identified with the Identify spell. This makes it a bit more of a puzzle to get the information, but the players have the resources to overcome it, which is much more satisfying than having everything not work because the story isn't ready for it. No one likes to run into invisible walls in what's supposed to be an open world.
Don't make any doors immune to Knock. A door might have a glyph that counterspells knock, but that glyph should be dispellable, the lock pickable, the door breakable, etc. Each of these may be challenging, but shouldn't be impossible. D&D is not a video game. In videogames, players accept that there are doors that are inexplicably unopenable until the story calls for it, because there are finite possibilities for what programmers can put into the games, and many of these limitations are not applicable to tabletop RPGs.
The players have versatile tool sets, and sometimes the DM's role is to "yes, and" even if it makes something easier for the players than the DM initially intended. The thing to remember is that these spells are limited resources the players have, and if they are willing to use them to identify objects and open doors, they have that much less to work with when they get into a battle later. These spells also take up spells-known or spells-prepared slots, so it burns twice as hard when a player is ex-post-facto nerfed by the DM at a point when the player was expecting to shine. If they run into rooms full of plant-monsters after the wizard all of his L2+ spell slots on disabling traps and opening doors, that will be a much harder fight than it would have been if the DM had saved those slots for Dragon's Breath and/or Fireball. They had it easer earlier, but at the expense of them facing greater challenge later. It's the DM's job to balance it out.
DMs can also put more locks on doors. Maybe a particularly important door has a half-dozen locking mechanisms on it, which makes it worth the players' time to find the keys or clues of how to open it, rather than brute-forcing it with magic. But if this is done, that should be observable, before the players start expending resources against it.
That's the same thing. Your artificially countering knock so it doesn't open the door. Put 12 locks on it, glphy to dispell... yeah you just made a knock proof door.
Your just arguing to flavor it better. And you did flavor it better.
We can just link to the threads on quantum ogres at this point. Yes a fully flushed out world that is always ready for players to where they want, and truly open is best. but sometimes the appearance of it is good enough and we don't all have the ability to have every path flushed out and ready to go. Sometimes that door is a hook for the next campaign.
Edit: To be clear the DM in this example is going to allow the player the infusion, they can absolutely use it in all the normal ways. This homebrew item meant to be OP and provide interesting choices and quest/story content just isn't going to interact with it. How ever you wanna flavor that "sure you materialize the lead shot, but there is no powder" OR "It's magical so you can't add an infusion to it" isn't itself a horrible violation of player agency/choice/nerf bat whatever.
I don’t have artificers, I do have guns, and I would have allowed it.
I have something akin to an artificer (a runewright), so that wouldn’t be an issue, and since my firearms are generally available (except, of course, the special ones, that it is a death sentence to have, blah blah) this would be a very high demand thing, lol.
that said, I have to side with the DM because his setting.
I dislike the ruling, though.
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