Martial weaponry and arcane magic are far too familiar, very rarely does one have magical weapons in their possession. Though, that never stopped the curious minds that thought to expand their use of weaponry and control over the arcane. 

With an untested weapon barely spoken or seen, you've taken on the task to advance such technology with magic. Although a dangerous feat, the controlled explosive force mixed with the wild nature of the arcane intrigues the thoughts of many. This archetype focuses on the ability to design, craft, and utilize the frightening energies of the arcane and the powerful yet dangerous ranged weapon that is still new and untested. 

It's time for a new age.

Inspired by: Shawn Ellsworth Fighter-Archetype-ArcaneGunslinger 5e | Miffbuster Dndbeyond 

(I already liked the mechanics for gunslinger, I just wanted to add a bit of magic.)

Explosive Properties

3rd-level Arcane Gunslinger

By creating and maintaining your firearms as well as becoming adept at magic, you gain proficiency with firearms and Arcana skills. This allows you to add your proficiency bonus to attacks made with firearms as well as any Arcana skill checks. Once you understand the basics, (following the Gunslinger properties), you can begin to use magic to aid you in combat. You gain proficiency with Tinker’s Tools. You may use them to craft ammunition at half the cost, repair damaged firearms, or even draft and create new ones (DM’s discretion).

Firearm Properties

Firearms are just as challenging as magic itself yet can be unique to your liking. Some properties are followed by a number and this number signifies an element of that property (outlined below). Firearms are ranged weapons.

Reload. The weapon can be fired a number of times equal to its Reload score before you must spend 1 attack or 1 action to reload. You must have one free hand to reload a firearm.

Misfire. Whenever you make an attack roll with a firearm, and the dice roll is equal to or lower than the weapon’s Misfire score, the weapon misfires. The attack misses and the weapon cannot be used again until you spend an action to try and repair it. To repair your firearm, you must make a successful Tinker’s Tools check (DC = 8 + misfire score). If your check fails, the weapon is broken and must be mended out of combat at a quarter of the cost of the firearm. Creatures who use a firearm without being proficient increase the weapon’s misfire score by 1.

Magic Mishap. Whenever you misfire with a firearm with Arcane ammunition (see more "ammunition" below), the attack will miss and the magical effects will fail to occur or bounce away harmlessly before doing so. When repairing your firearm after a magic mishap, you must make a successful Tinker's Tools check and Arcana check (DC = 10 + misfire score). If your Arcana check fails, the weapon will not be able to handle Arcane ammunition until you properly fix it out of combat. If your Arcana check succeeds, you won't be able to use Arcane Ammunition until your next turn unless you roll a Nat20.

Ammunition

All firearms require ammunition to make an attack and their rare nature makes it impossible to find or purchase. However, you can craft ammunition yourself using your Tinker’s Tools at half the cost. In addition, your knowledge of some magic allows you to infuse your ammunition with magical effects (see "Arcane Ammunition Options"). Each firearm uses its own unique ammunition and is generally sold or crafted in batches listed below next to the price.

Firearms

Name	Cost	Ammo	Damage	Weight	Range	Properties
Palm Pistol	50g	2g (20)	1d8 piercing	1 lb.	(40/160)	Light, reload 1, misfire 1
Arquebus	50g	4g (20)	1d8 piercing	7 lb.	(60/240)	Reload 1, misfire 1
Pistol	150g	4g (20)	1d10 piercing	3 lb.	(60/240)	Reload 4, misfire 1
Musket	300g	5g (20)	1d12 piercing	10 lb.	(120/480)	Two-handed, reload 1, misfire 2
Pepperbox	250g	4g (20)	1d10 piercing	5 lb.	(80/320)	Reload 6, misfire 2
Blunderbuss	300g	5g (5)	2d8 piercing	10 lb.	(15/60)	Reload 1, misfire 2
Rifle (hunting)	Crafted	20g (10)	2d10 piercing	8 lb.	(80/240)	Two-handed, reload 6, misfire 3

Magical Effects

3rd-level Arcane Gunslinger

Arcane Ammunition. You learn to imbue magic into your ammunition that enhances a firearm attack against your enemies or aid your allies. You learn three Arcane Ammunitions of choice which must be prepared. (Look at options under "Arcane Ammunition Options")

You learn additional magical effects of your choice at 7th, 10th, 15th, and 18th level. Each time you learn a magical effect, you can replace one effect you know with a different one.

Wit. Despite preparation, you gain a number of wit points equal to your Wisdom modifier (minimum of 1) to determine your quick actions in applying your magical effect into your firearm. You regain 1 expended Wit point each time you roll a 20 on the d20 roll for an attack with a firearm or deal a killing blow with a firearm to a creature of significant threat (DM’s discretion). You regain all expended Wit points after a short or long rest.

Saving Throws. Whenever your arcane ammunition requires a save, the saving throw DC is calculated as follows:

   Arcane Ammunition save DC = 8 + your proficiency bonus + your Intelligence modifier

Rapid Reload

7th-level Arcane Gunslinger feature

After learning the basic properties of firearms, you've learned how to quickly reload. As a bonus action, you can reload any firearm.

Happy accidents

10th-level Arcane Gunslinger feature

You learn how to quickly attempt to fix a jammed gun whether under magical effects or not. You can use one Wit point to attempt to repair a misfired (not broken) firearm as a bonus action.

Quick hands

10th-level Arcane Gunslinger feature

In a rush of adrenaline, you attempt to speedily fix your firearm. While repairing a misfired firearm using either a Tinker's Tools check or Arcana check, you can add an additional 1d6 to the score to either check only once. Once you use this feature, you can't use it again until you finish a short rest.

Runner-up

15th-level Arcane Gunslinger feature

You add your proficiency bonus to your initiative. If you are first in battle, Arcane ammunition becomes available and ready to use immediately. If you do not use the Arcane ammunition, you temporarily gain 1 Wit point.

Magic Infusion

18th-level Arcane Gunslinger feature

You've become adept in your craft and decide to mix magic and metals. You gain access to creating firearms with any magical effect from the Arcane Ammunition options. For one firearm of your creation (given the cost and materials you need), you can add only one Arcanic Ammunition magical effect. After choosing a magical effect, the firearm will have the ability to use that magical effect without the need to use Wit points. 

To change the magical effect of your firearm, you must do so during a short or long rest and make an Arcana skill check (DC = 10 + Proficiency bonus + Intelligence modifier). On success, you replace the magical effect. On a fail, you still have the effect and are unable to replace the magical effect until the next long rest.

If you lose this firearm, you can create a new one over the course of three days of work (eight hours each) by expending 50 gp worth of metal and other raw materials.

Rupturing Hit

18th-level Arcane Gunslinger feature

 Your firearm attacks score a critical hit on a roll of 19-20 to which you can regain a Wit point on a roll of 19 or 20 on a d20 attack roll. When you score a critical hit on an attack with a firearm, the target will suffer an additional half of the damage from the attack at the end of its next turn.

(Literally Hemorrhage Critical and Vicious Intent because I actually like this feature)

Arcane Ammunition Options

These magical effects are presented in alphabetical order.

(Inspired by: Shawn Ellsworth)

Agonizing Shot

You infuse necromantic magic into your shot when you expend 1 Wit point. On a hit, the creature must make a Constitution saving throw or get an additional 2d6 necrotic damage. They also cannot regain any hit points until the start of your next turn. The damage increases to 4d6 at 18th level.

Blinding Shot

You can infuse evocation magic into your shot by expending 1 Wit point. When it hits the creature, it will flare with bright blinding light. The creature hit must succeed on a Constitution saving throw or suffer disadvantage on attacks until the end of their next turn.

Chain Shot

When you make a firearm attack against a creature, you can expend one Wit point to attempt to bring the creature closer. The end of a bullet becomes a conjuration of an arrowhead with a chain connecting back to the gun. On a hit, the creature must make a Strength saving throw or be pulled until they are 10 feet away from you.

Freezing Shot

When you make a firearm attack against a creature, you can expend one grit point to freeze a creature. On a hit, the creature must make a Constitution saving throw or take an extra 2d6 cold damage. The creature's speed is halved and cannot use reactions, at the start of the creature's turn, they can make a Constitution saving throw to try and get out of it. They only take extra damage from the initial shot. The damage increases to 4d6 at level 18.

Healing Shot

When you make a firearm attack against a creature, you can expend one wit point to fire an explosive fume of healing properties. On a hit, a creature does not take any damage and instead regains 2d6 hit points. Any creature 5 ft from the shot, whether it shot a creature or not, regains 1d8 hit points. Does not affect undead or constructs.

(Imagine it's like a shot from a doctor)

Hellish Shot

When you make a firearm attack against a creature, you can expend one Wit point to burn a creature. On a hit, the creature takes damage and must succeed on a Constitution saving throw or take additional 2d6 fire damage. At the start of every turn, the creature must continue to make a Constitution saving throw or take another 2d6 fire damage until they are successful.

Multi- Shot

When you make a firearm attack against a creature, you can expend one or more Wit points to enhance the volatility of the attack. In one shot, for each wit point expended it adds an additional bullet that hits any creature of your choice. Any creature within the cone must make a Dexterity saving throw or take an additional 1d4 force damage for each additional bullet.

Pressure Shot

When you make a firearm attack against a creature, you can expend one Wit point to force a creature back. On a hit, the creature will not take normal damage and instead, half the attack as bludgeoning damage, they must succeed on a Strength saving throw or be pushed 15 feet away from you. 

Searing Shot

When you make a firearm attack against a creature, you can expend one Wit point to fire the equivalent of a bright and blinding fireball. On a hit, the creature must make a Constitution saving throw or take 1d6 radiant damage and become blind until the start of your next turn.

Thunderous Shot

When you make a firearm attack against a creature, you can expend one Wit point to electrocute a creature. On a hit, a creature must succeed on a Constitution saving throw or take additional 2d8 lightning damage. Any creature within 10 ft of the target must also make a Constitution saving throw or take 1d8 lightning damage. The damage increases by 4d8 on target and 2d8 area effect at 18th level.

Toxic Shot

When you make a firearm attack against a creature, you can expend one Wit point to poison a creature. On a hit, the creature must succeed on a Constitution saving throw or take additional 1d6 poison damage. The damage increases to 3d6 at level 18.