How powerful are these homebrew firearms?

Question

I am basing the structure off of this post about homebrew.

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Problem

One of the players in my game is very interested in playing a character with guns. We talked about which aspect of such a character he wants to play and he decided on a character that crafts and invents guns and then uses those guns in battle. We looked at various options for something like this (currently just looking for weapons not the class) and sadly none really fit the idea he was going for. The DMG guns are much too op to be used as his character's main weapons. Matthew Mercer's guns are more balanced, but the main problem is the misfire feature. Just from a design perspective, the misfire feature disincentivises/punishes players just for attacking, when the opposite should be true. I understand that it was designed for a specific player, and is not meant to work for ever table. Hence creating custom ones.

Balance

The reason I am posting this on here is to judge the relative power level of them. I'm not looking for them to be "balanced" with the base weapons per se because we are using quite a bit of homebrew and everyone at the table has a power level boost. I just want a vague idea of roughly how much more powerful than default these are (obviously some are clearly better than others, this is by design) based on individual weapons or groups of weapons. How powerful are they and are there any shenanigans my players can get up to?

Context

Just to provide some content, the party consists of the gunsmith, who will be using these as their main weapons, and will start out with a hand pistol and a blunderbuss. They can add modifiers to weapons as a class feature, such as longer range, faster reload, more damage, ect. This scales with level, so at higher levels they can fit more/better modifiers onto their guns. They are most interested in using blunderbusses, shotguns, cannons, ect, because they are a short halfling and think the size difference would be funny. No other characters in the campaign, player or npc, get access to firearms really.
The other 2 party members are:

• A paladin with a homebrew 2D8 greatsword that attacks slower than normal and has a nerfed GWM feat.
• A light domain cleric who will at later levels be able to fly and have a magic fire spear.

In the campaign as a whole, I am using a lot of homebrew. Better criticals, minor inspiration, lots more homebrew weapons, homebrew feats, the paladin gets cool manoeuvres inspired by battlemaster, ect. Most stuff is allowed if the players ask and it seems balanced with the rest of the campaign and if it seems cool.

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Firearms Rules

All these weapons are firearms and have some rules governing their use.

Elegant

All firearms use the wielder's dexterity modifier for attack rolls. Do not add an ability modifier to damage rolls.

Hard to Load

Unless you have proficiency in these weapons, each gun takes longer to reload. If the weapon takes a bonus action to reload it now takes an action, and if it takes an action or more, it takes 1 extra action.

Ammunition

All firearms expend a piece of ammunition each time they are fired. Each weapon uses a different ammunition, found in the ammunition column of the firearms table. This ammunition cannot be recovered after being fired.

Piercing

All firearms deal piercing damage unless specified otherwise.

Range

I will be writing ranges as either Very long, Long, Medium, Short or Very Short. This is just to make it easier and faster for me. Each range represents an actual range.
Very Long - 150/200
Long - 100/150
Medium - 50/100
Short - 25/50
Very Short - 10/25

Properties

Capacity (X)

Fire X times before reloading. When you have fired X times you cannot fire again until the weapon is reloaded.

Reload (X)

You must spend X amount of time to load ammunition into the weapon.

Multiattack(X)

Regardless of how many attacks you can normally make, when you take the attack action with this weapon you make up to X attacks.

Spread

This weapon fires a cone of ammunition. Make separate attacks against each creature in the cone.

Black Powder

This weapon cannot fire when wet or exposed to water. Dries in 1D4 hours. Automatically fires if loaded and exposed to flame or sparks.

Heavy

You need 14 strength to wield a heavy weapon, otherwise you have disadvantage on attack rolls.

Superheavy

You need 17 strength to wield a superheavy weapon, otherwise you have disadvantage on attack rolls. If your strength is less than 14 you cannot wield the weapon.

Unliftable

This weapon is too heavy to lift, but it can be dragged around at half your movement speed or placed onto carts.

Firearms

Name	Damage	Capacity	Multi- attack	Reload	Properties	Ammunition	Range
Hand Pistol	1D4	1	1	1 bonus action	Light, Concealable	Small Cartridge	Very Short
Pistol	1D10	1	1	1 bonus action	Light	Small cartridge	Short
Flintlock	1D12	1	1	1 action	Blackpowder	Gunpowder and Shot	Short
Rifle	2D8	1	1	1 action	Two-handed	Medium Cartridge	Medium
Blunderbuss	3D6	1	1	2 actions	Heavy, Blackpowder, Two-handed	Spreadshot and Gunpowder	Very Short
Shotgun	Variable	1	1	1 action	Special, Two-handed, Heavy	Variable	Variable
Double Barrel Pistol	1D8	2	2	1 action	-	Small Cartridge	Medium
Double Barrel Rifle	1D10	2	1	1 action	Two-handed	Medium Cartridge	Medium
Double Barrel Shotgun	Variable	2	1	1 action	Special, Two-handed, Heavy	Variable	Variable
Revolver	1D8	6	2	1 action	-	Medium Cartridge	Long
Sniper Rifle	2D12	1	1	2 actions	Two-handed, Heavy	Large Cartridge	Very Long
Magazine Rifle	1D10	8	2	1 action	Two-handed	Medium Cartridge	Medium
Heavy Revolver	1D12	6	1	1 action	-	Large Cartridge	Long
Magazine Pistol	1D6	9	3	1 action	Light	Small Cartridge	Short
Cannon	Variable	1	1	6 actions	Special, Unliftable, Two handed	Variable	Variable
Mini Cannon	Variable	1	1	3 actions	Special, Superheavy, Two handed	Variable	Variable
Mortar Launcher	1D12 + 3D4	1	1	2 actions	Superheavy, Two handed	Mortar	Special

Special Weapons

Shotgun + Double Barrel Shotgun

You can load and fire a variety of different ammunition types from this gun.

Ammo types:
Shells - Spread, 2D4 piercing, Very Short range
Slug - 1D12 piercing, Long Range
Explosive - 1D10 piercing + 1D4 fire, Medium Range
Dragon's Breath - 3D4 fire, Very Short range

Mortar Launcher

Target a location within 40 feet of you. The mortar lands there and deals 1D12 bludgeoning damage to any creatures there. It then deals 3D4 fire damage to creatures within 5 feet, 2D4 fire to creatures within 10 and 1D4 to creatures within 15. It flies in an arc, it's apex moving 5 feet upwards for every 5 feet to your target.

Cannon

Multiple people can load this weapon at once, up to a maximum of 3, and it is not affected by the hard to load rule. You can load and fire a variety of different ammunition types from this gun.

Ammo types
Cannonball - 6D12 bludgeoning, Long Range
Grapeshot - spread, 5D4 piercing, Medium Range

Mini Cannon

Multiple people can load this weapon at once, up to a maximum of 2, and it is not affected by the hard to load rule. You can load and fire a variety of different ammunition types from this gun.

Ammo types
Cannonball - 2D12 bludgeoning, Medium Range
Grapeshot - spread, 3D4 piercing, Short Range

Extra Info

(mainly used for answering questions in comments)

Crossbow expert does not affect these.

Answer 1

Generally less powerful, at best more complicated

I'll start with how to evaluate a weapon compared to the vanilla ones, or at least how I'll be doing it.

• We'll assume a character that is planning to use weapons. That means we have an ability modifier between 3 and 5 (depending on level) and that it will get Extra Attack. (If not, you'll need to the more exact analysis with the specific situation.)

• Find the most similar existing option, and use as your benchmark.

• Relevant for the kind of properties you have, we'll assume a character is using this weapon and it alone (ie. no swapping etc.). For cases where that is too much of a stretch, it needs to be evaluated as a different kind of option (but I'm getting ahead of myself.)

Now I think there's a couple of your rules/properties that's worth really breaking down:

Elegant. Ranged weapons use Dexterity for attacks anyway, though making that explicit isn't bad per se. But armed with that we can reduce the rule to:

You don't add your ability modifier to the damage rolls of firearms

This means that damage evaluations won't be one-to-one with other weapons. Since it'll be useful later, a modifier between 3 and 5 (again, depending on level) is in the neighborhood of a d6 or d8 on average (3.5 and 4.5 respectively). So in very rough terms, a normal 1d8 weapon would be about equivalent with a 2d8 elegant weapon.

It is worth mentioning that having more of the damage as dice means the weapons benefit more from crits, though the effect of that is generally between 5% and 10%.

The more direct comparison is to cantrips, except cantrips aren't expected to deal high as consistent damage (since users of cantrips will also have full on spells).

Multiattack (X). So this property does some strange things. At X = 1 it is equal to the loading property (except you can't use a existing feat to ignore it), which is bad once we get Extra Attack. For X = 2 it's better at T1 when we don't have Extra Attack, it doesn't really do anything once we do, and gets bad once we get Extra Attack(2) (eg. 11th Fighter). Equivalent for higher levels of X.

The issue you're gonna run into with evaluating this is that you can't balance a multiattack weapon to work across the tiers of play. Since multiattack wholly breaks the damage scaling from Extra Attack, it's impossible balance the same weapon to be balanced at both T1 and T4 (or any in between), as is the case for normal weapons. If sticking to this pattern, you'd need to split the weapons between different tiers of play (ie. Extra Attack numbers) and work from there.

Onto the specifics

We can lump together the hand pistol, pistol, and flintlock. These are most similar to the hand crossbow, except that is has more damage (let's say ~2d6 equivalent), greater range, doesn't require a bonus action (or action) to reload, and has distinct synergy with Crossbow Expert. And outside of that feat synergy, the hand crossbow is generally worse than the other crossbows and the longbow (or short bow for that matter, since that doesn't have the loading property).

The rifle is relevant to mention, since it has par damage with a longbow, except that you have to reload using your next action, bringing us back to the same awful.

Anything else which makes straight attacks, and where the multiattack number times the damage die count (MA×DDC) equals 1 has the same problem as the pistols. Capacity and Reload don't really matter, because the base damage before those drawbacks is lower than the expected damage with a normal bow or crossbow. This covers the double barrel rifle and heavy revolver. Where the product of those equals 2 we have the same problem as the rifle, with a strength dependent capacity and reload. The easiest way to evaluate these is taking the capacity divided by multiattack as how many rounds the weapon can par normal weapons. For example, a revolver is about equal to a longbow in a fight 3 rounds or shorter.

The exception to the above is that the sniper rifle has slightly more damage than a heavy crossbow (closest equiv), though if the fight is more than one round (which is a pretty safe assumption), the damage output props off like a rock. I also feel obliged to point out that your sniper rifle has a worse range than a longbow, at 150/200 compared to 150/600.

The magazine pistol is the only of these weapons that's better than the normal equivalent, having a MA×DDC of 3 it can sustain for 3 turns. It would have an expected (raw) damage of 10.5 (not counting crits) compared to a hand crossbow's 6.5. That raw damage is actually in the area of greatswords and mauls (without the fighting style) or a rogue with Sneak Attack (1d6) which would be fairly strong during T1. Especially since you have way less restrictions than those approaches, and if you hope to never reload, you'd even get away with a shield.

Once you get Extra Attack (ie. 5th level or higher) you'd need a MA×DDC of 4 for parity with a longbow.

Shotguns

Now we get to blunderbuss and shotguns, which use the spread mechanic (the non-spread ammo types for the shotguns can be evaluated the same as normal weapons described above). One design thing which makes the comparison difficult is that your implementation for a cone effect is different. The normal 5e solution is to force each creature to make a (Dexterity) saving throw, often taking half damage on a success. This isn't that.

If we ignore that and consider that a 25 foot cone but you have disadvantage beyond 10 feet (actually, with how ranged attacks within 5 feet works, you probably have disadvantage unless the target is exactly 10 feet away from you) equivalent to a 15 foot cone forcing a save and taking half on success, firing the blunderbuss is about equal to casting burning hands. Making the common optimization assumption that AoE effects hit two targets, spending 3 actions for a 1st level spell is about par with a T1 bow user (6d6 over 3 rounds). Normally that's the kind of about par where I'd say go playtest it, but in this case I'll warn that I expect the two turns where you don't do anything to be really boring. Also specific to your half-ling, since they are small and the blunderbuss heavy, they'll have disadvantage on all their attacks with it. Shifting over the spread weapons to use a save would mitigate some of its issues.

For the shotgun using the same evaluation you get 4d4 over two turns, as opposed to the 4d6 a bow user would deal (possibly more). So you pretty much get a worse range and damage for the complicated mechanic.

Cannons

I'm not sure these are worth covering in detail. The cannon is structured pretty much similar to a siege weapon, the same as the one in the DMG. It fires the equivalent of a 4th level spell (or 2nd level for the AoE) going by the DMG guidance on creating spells (in Chapter 9).

The mini cannon is maybe more interesting, though its modes are either a sniper rifle with less range and longer reload, or a blunderbuss with less damage, slightly bigger range and longer reload.

The mortar's attack is probably best looked at as a better ice knife, I think landing at 2nd level. And a 2nd level spell for two actions is fairly suspect. And that's assuming there are normal to hit rolls/saving throws, which isn't quite clear. And if not then it's very powerful.

Specific Suggestions

You're designing for a specific player character. Focus on the things that player/character needs, and make those work. If they want blunderbusses and cannons, don't bother with 10+ weapons that aren't that.

As much as possible, find an existing option and reflavour that as the weapon(s) or features you need. It'll save a lot of work, both in matching the damage and in getting mechanics that are good for gameplay.

Since your table already has some powerboost and homebrew, find something you like reasonably and tune it if it turns out to be too powerful (or not powerful enough). I trust your Social Contract (as you discussed in Session 0) includes the option for things to be retuned, it's quite common (and needed) when including homebrew content.