Getting around the damage of the explosive knight can be a bit tricky, since we are so used with weapons that do continuous damage we see the firearms and think immediately that they are absolutely broken, but if we take reload into account the damages are quite different from what it seems, remember that you don’t only lose the weapon damage, but also the dexterity score, here is a table with the damage per attack taking reload into account, that supposes 20 dexterity for easy comparison.
And here is a table of the damage of the gatling gun considering the misfire and the probabilities to get to a certain amount of stacks.
We can see that the damages are between the level of a longbow and heavy crossbow, but not only that, these weapons have a misfire score that thought does not affect the damage (except for the gatling gun) they affect very heavily the course of battle, and can leave you disarmed, prone or without enough movement to go to safety.
Another thing to consider is that these weapons have different requirements for shooting and far shorter ranges than normal ranged weapons, which will leave you a lot of times at very close range where you are not only less effective but also in danger since you are more fragile that melee fighters because you are a Dexterity build and don’t have a shield, but also because your Constitution will be lower because you need a decent Intelligence score and will be maxing Dexterity.
But obviously you are not just shooting with one firearm since you start a fight with all your firearms loaded, a good explosive knight then knows how to use all his weapons in a combat effectively to get the most damage possible and minimize the risks of the firearm. But as rounds go by your damage output declines since your ammo in all the weapons by round 3 should be empty at any level, also action surge is not as effective in the explosive knight as in other fighter subclasses since you will burn out your ammo quicker and you only have one object interaction per turn to switch weapons.
Is also important to remember that your level 3 feature is the ability to get access to these firearms plus some tactics that are like maneuvers but with a weaker effect and without the extra superiority dice damage or at least that was the intention.
Damages by round Simulation
For this comparison I just took the damages of the most powerful firearms (wall gun, rifle, mortar, pistol and avoided the gatling gun for simplicity) in a perfect scenario without misfires and that you can switch between weapons without having to deal with the requisites, the ranges, or the object interactions. I also did not use any features like the tactics, tactical roll, the explosives, and walking arsenal, (but I will talk about the later), also I did not consider any feats or race features, except for crossbow expert which is necessary for a good comparison.
You can see that if you can get the most out of weapons you can get a lead in terms of damage, but it is still it is not that crazy and remember that this is an imaginary scenario that will be impossible in a real combat since it does not consider the misfires (also remember that as you get more attacks this chance increases), the requisites and range. I also added a tactical roll as an extra wall gun shot for comparison at the right. Tactics have a weaker effect than the battle master maneuvers, but even if we treat them as the same, a battle master can still add extra damage from their superiority dice which is at the side of the table taking level into account, and that is without martial adept or fighting initiate that gives another two dice, also a battle master recharges his superiority dice per short rest instead of long rest like in the grit points.
In term of feats the explosive knight does not get the same value of things like sharpshooter extra damage since it gets less attacks considering reload, and missing a shot is a lot worse for the explosive knight so the -5 is very risky plus you have very few ways of getting advantage, still sharpshooter is a must because the range increase and the ability to avoid some cover is decent too. There are also more feats that tip the balance in favor of subclasses like a battle master, especially for melee builds (great weapon master, polearm master, fighting initiate, martial adept, sentinel, and others). Though the new Piercer feat from Tasha’s is an amazing choice for the explosive knight along with lucky to avoid some misfires, fey touched can give you intelligence and a misty step along with a hunter’s mark, athlete is actually decent since it gives you dexterity and the ability to get up from prone at just 5 feet, mobile gives you more movement which is pretty good and also since the palm pistols count as melee at 5 feet you can run without provoking opportunity attacks, though can be good if you are too squishy, if you are an elf elven accuracy is amazing if you have someone that can give you advantage and if you go halfling probably second chance and squat nimbleness are decent options. Still take in consideration that you need to max Dexterity and I recommend at least a 14 or 16 score in Intelligence.
Explosives and fired up.
What about the explosives? Well, the explosives are in the same category of a 3rd level spell in terms of power, so expending a whole action at level 10 to use them is not that amazing, and are a lot worse after 11th level since you get three attacks, but they are more utility based and have AOE so you can find a good use for them if there is a group of enemies or if you don’t have more ammo in your weapons and think the fight is going to end soon.
But at level 15 you get the ability to spend 2 grit point to use one explosive as a bonus action, this sound way to powerful, but think of what an explosive knight and a battle master could do with 2 tactics/maneuvers, he could use riposte 2 times which is (4d6+10+2d10) damage with a great sword for example, or you can get +20 damage with deadeye shot and sharpshooter. Not only are you going to melt your grit points for the day (you will at most get 11 if you have 20 INT) but also you only have just three explosives a day.
The last feature Walking arsenal seems like free damage every round, but it is a bit more tricky to pull off than it seems, first you have to remember that you only get one object interaction per round, so you only have one switch, and also you add the 2d6 to your next attack only if it hits, if it misses the extra damage is no longer available, also some weapon switches are almost impossible to pull off, like going from the wall gun to the blunderbuss, if you are going with the gatling gun switching weapons means that you will lose the stacks, if you get the misfire from the pistol you will have to use your object interaction to pick it up, and with the rifle you lose your object interaction. so, you will have to manage what you want to do to get the extra 2d6 and work around the different ranges, requisites, and misfires.
Firearm positions and purposes:
The palm pistols are a tricky thing to balance, since it has the light property it allows you to do an extra attack as a bonus action, this can be very powerful at the start but gets weaker and weaker as you get extra attacks. You start a fight with both pistols loaded, but after that you have to reload each one individually, making them the firearms with the lowest damage, but they have a few amazing uses, first you can conceal them in your sleeves, this serves in roleplay but you may also get a surprise round if your DM allows it, also you can attack normally with any firearm and switch to the palm pistols to do an extra attack as a bonus action or reload one of them as a bonus action, but remember that they have a very short range so you will have to get very close to get the value, but a good thing is that you don’t have disadvantage at 5 feet. The bonus actions are quite important to the explosive knight since you require it for the gatling gun, the more powerful tactics, to use explosive objects quickly, do a tactical roll, second wind, and more if you get magical items or feats that use it. So, this weapon consumes that use and the misfires restrict your options by taking your bonus action next turn.
the classic is a double barrel pistol that allows you to move easily in combat by giving you 5 feet more movement per attack, it has a medium damage and a short/medium range allowing you weave in and out easier than the any other firearms (still the range is less that the one of a hand crossbow which isn’t much), the misfire throws the pistol back from the recoil, making you having to move 5 feet back and use your object interaction to retrieve it this can take your ability to switch firearms that or next turn, or you can leave it there and switch to another weapon depending on the situation. The pistol works great with almost any other firearm, since it allows you to have more movement, which allows you to get in better positions or in range, have movement after standing up from being prone and run away, and having the movement for the rifle requirement.
The last resort is a short blunderbuss that works at very short range and has a very short cone, it also has one of the lowest damages of the firearms, but it has the potential to hit more than one creature. but the biggest purpose of the weapon though it is the ability to get you out of melee, if you have a creature at 5 feet you can shoot it without disadvantage, and get pushed back 5 feet, which does not trigger attacks of opportunity. But be careful because the misfire leaves you prone, so if you start your turn 5 feet from something you will only have 15 feet left to move if you misfire, or if you use your movement to get close to get that sweet two targets cone you may not have enough movement to stand up from being prone if you misfire and end up in a very dangerous position and probably will have to expend grit points or a tactical roll to avoid it.
The hand mortar is a very flexible firearm, covers a medium distance of 30 feet in total, the first 15 feet allows you to hit a creature doing extra damage and pushing it 5 feet (which can combine well with some explosives and tactics), this damage is about the same as the blunderbuss, but after the 15 feet it explodes allowing you to do damage to more than one creature, this damage is lower but getting this to hit multiple targets is a lot easier than the blunderbuss, thought you will need a lot of movement to position yourself correctly. The misfire halves your movement, which can be problematic to get in range with shorter firearms like the blunderbuss, the pistol, the gatling gun and the palm pistols, but also you will have problems standing up from prone, running away, the rifle and wall gun prerequisite and getting in a good position with the mortar.
The long dead is a wall gun that has the biggest damage and range of all the firearms (though still its maximum range is 60/80 feet, which is very low compared to the 150/600 of the longbow or the incredible 200/800 bad news from mercer gunslinger ), but this firearm has the harshest prerequisite and misfire, to use it without disadvantage you need to position yourself in the ground which requires half your movement, and you count as prone while in this state, which means that you would have to use all of your movement to just get down and stand up so you aren’t prone, and If you use any of your movement to get into firing range you will end up prone since won’t have enough movement to get up (also remember that you still have disadvantage in this position with other firearms), the misfire is very harsh since it reduces your range to half (this doesn’t affect the blunderbuss or mortar), so your next turn you may not be able to reach the target with the wall gun or other firearms so you will have to get closer (which can be more difficult if you finished in the prone position of the wall gun).
The gatling gun is a complicated weapon to evaluate, it works best at short range and it has the biggest potential damage since it also gives you an extra attack as a bonus action, but to get the most out of it you need to get to up to 5 stacks which is a lot more difficult than it seems (you can see the table for the probabilities), you start doing the same damage as a dagger and go up from there up to 5d4+dex, since the ammo consumption goes up with stacks you can only make 4 attacks (1+2+3+4=10) before having to reload and after that you can make 2 powerful attacks (5+5=10) until you lose the stacks. You lose stack in almost every way except for reloading, so if you are 5 ft to an enemy you might not be able to attack it next turn with your maxed stacks, so a good idea is to unload everything with an action surge or use a tactical roll since it does not count as movement and lets you get out of someone at 5 feet to avoid disadvantage. But even then, you are still in the hands of lady luck praying that you do not get the misfires and will probably have to expend a few of your tactics to try to protect your stacks.
The rile at first glance seems like a better pistol in terms of damage and range, but this is a deceptive firearm, the requisite to shoot this firearm is that it consumes 10 feet of movement, that means that at level 5 or 11 you need 20 feet of movement to attack normally, this can be quite difficult considering the range of other weapons and the misfires that take movement or leave you prone, so this weapon is best when you only take one shot and switch to another one or use it in conjunction with the pistol. Also, the misfire is harsher than the pistol since it does not allow you to switch weapons next turn, so you need use your switch this turn to prepare for the next turn, or if you already used it, be stuck with the rifle.
So that is it, I could get a lot more into depth about some things like talk about specific tactics, explosives or ammo, but I think that is enough to get my point across in how I balanced and designed this subclass, the explosive knight at the end of the day works in a very high-risk high-reward playstyle, a lot of times you will have to take your chances but also this subclass requires a very strategic thinking in terms of positioning and a lot of management of resources.
Also remember a few things, this is another firearm system completely different than the one at the DMG (like the mercer gunslinger one), so the gunner feat does not let you ignore the reloading property since the explosive’s firearms do not have the loading property, you only get the benefit of not having disadvantage at 5 feet. The same its true for the artificer infusion repeating shot, you do not get to ignore the reload property.
Probably when reading this subclass you immediately thought in playing it with a halfling, I thought of making a firearm heavy to prohibit this, but I do not think a halfling is broken, you can play whatever you want, I do not want to restrict players to much and picking a race to avoid a few misfires is a solid strategy, but remember that a halfling has a speed of 25 feet so you may encounter a few problems getting in range or some requirements.
Why I created the subclass.
I was about to play in a campaign of a friend, and I thought about playing the gunslinger from matt mercer, but as I was looking at it, I found a lot of things that I did not like and when searching about opinion about the subclass and other homebrew gunslingers I seem to find very similar opinions in the problems.
So, first off is the firearms, they usually do not have any personality and feel more like a bow/crossbow reskin, so I wanted to design firearms that were powerful, but with their own limitations, that felt different from other weapons with their own strengths and weaknesses, but also that you would have to deal with the reload. A lot of people make the reloading part of firearms not important since you can just use a bonus action to reload or just get multiple weapons of the same time, that is why I made this subclass in a way that you can craft a limited number of firearms so that you will have to deal with reloads, and your power is not based in the amount of gold that you have so you can buy multiple firearms.
Another issue that I had is the misfire, most people do not like critical fumbles, and the feeling that I got from mercer’s and other misfires is even worse than that, an auto miss that also left your weapon useless feels super bad and is an awful balancing idea in my opinion. But the biggest problem is that people get around the misfire by buying multiple firearms and just dropping the broken one just like with the reload, or some people make it a bonus action to repair so it ends up not mattering at all. So, I designed misfires that are a lot more common but without feeling horrible, they are inconveniences that you will have to play around and deal with.
For anyone interested in using this subclass this is how I put the features and firearms in roll20 in the campaign that I’m playing this subclass in.