Is this homebrew gunslinger class balanced?

Question

I have been homebrewing a gunslinger class for a player who wanted to play one, but the problem is I couldn't find any that gave exactly what we wanted. I based it off one I found somewhere and made some tweaks, but I'm not sure if it's balanced or not, and it only goes up to level 10.

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Gunslinger

Level	Proficiency Bonus	Features	Grit Points
1	+2	Wary, Skill shot	2
2	+2	Shooting Styles	2
3	+2	Gunsmithing	3
4	+2	Ability score improvement	4
5	+3	Extra Attack	5
6	+3	Ability score improvement	6
7	+3	Trail Feature	7
8	+3	Ability score improvement	8
9	+4	Skill Shot (2)	9
10	+4	Bullet time	10

Class Features

As a Gunslinger, you gain the following class features

Hit Points:
Hit Dice: 1d8 per Gunslinger level
Hit Points at 1st Level: 8+Constitution modifier
Hit Points at Higher Levels: 5 (1d8)+Constitution modifier

Proficiencies:
Armor: light armor, medium armor
Weapons: simple weapons, pistols, revolvers, rifles, shotguns
Tools: Tinker's tools, Smith's tools
Saving Throws: Dexterity, Wisdom
Skills: Choose three from Acrobatics, Athletics, Perception, Sleight of Hand, Stealth and Survival.

Equipment
You start with the following equipment, in addition to the equipment granted by your background:

• (a) a revolver, (b) a smoothbore rifle, (c) a blunderbuss or (d) two pistols,
• A hand pistol
• 50 rounds of ammunition
• 3 grenades
• A set of tinker's tools
• A small notebook with weapon designs
• A small pouch of gunpowder, enough to make 50 more rounds of ammunition

Features

Wary

Gun fights and ambushes have taught you one thing, and that's to be alert and watchful. You can't be surprised while you're conscious.

Grit

Your way of life has caused you to develop a particular hardiness to your person called grit. This is represented by the number of Grit points you have, which can be seen on the Gunslinger class table.
You can expend Grit Points to perform abilities called Skill Shots, with you regaining all expended Grit at the end of a short or long rest. At 1st level you know 2 Skill Shots, and you learn 2 more at 9th, and 17th levels. Some Skill Shots may call for an enemy to make a saving throw, if that is the case, the following is the DC for the saving throw called. Additionally, only one Skill Shot may be performed per turn.

Skill Shot Save DC = 8 + your proficiency bonus + your Dexterity modifier

Shooting Styles

At 2nd level, you develop a particular style of shooting and using firearms. Choose one of the styles below. You can't choose a Shooting Style again, even if you later get to choose again.

Dual-Wielding
When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack so long as the attack is made by a firearm.

Explosive
When you use an explosive, grenade, or a weapon with the Explosive property, you can reroll 1s and 2s on the damage die, though you must take the new rolls even if they are 1s and 2s.

Heavy Caliber
Attacks you make with two-handed firearms deal +2 bonus damage.

Marksman
You have a +2 bonus to attack rolls made with firearms and do not incur disadvantage on attack rolls due to range

Gunsmithing

Beginning at 3rd level, you can craft firearms. To craft a firearm, you must first have the schematics for it. Every 2 levels starting from 3, you can learn a new firearm schematic. Pick any basic firearm and add to it (if you wish) a number of modifiers equal to your proficiency bonus.
To craft the firearm, it takes a number of days equal to the base firearm's crafting time plus extra time for each modifier you apply. You must have access to raw materials worth at least half of the firearm's cost, which are expended in this process, as well as the extra price added by each modifier, and access to the facilities needed to craft the firearm. You can also add modifiers to existing firearms up to a total of your proficiency bonus.

Ability Score Increase

When you reach 4th level, and again at 6th, 8th, 12th, 14th, 16th and 19th level, you can increase one ability score of your choice by 2, or two ability scores of your choice by 1. As normal, you can't increase an ability score above 20 using this feature.

Extra Attack

Beginning at 5th level, you can attack twice, instead of once, when you take the Attack action on your turn.

The number of attacks increases to three when you reach 13th level in this class.

Bullet Time

Starting at 10th level, your senses become so honed that you can momentarily perceive time slower. Once per long rest, you can use your bonus action to enter Bullet Time. For the next round, you gain advantage on Dexterity saving throws and Perception checks, and can use your reaction to make a number of attacks equal to your Dexterity modifier. Once you use this feature you can't use it again until you finish a long rest.

Answer 1

Depending on your group, it may not matter if it goes up to level 20 as a lot of groups campaigns dissolve before that point especially with new players.

Along with this, this class is at least partially inspired by Matthew Mercer's Gunslinger which isn't official, but normally widely respected (though I can't say for this class specifically). As a result you may be better using that which is a archetype of fighter, likely very balanced, and fully formed.

Before going through the entire thing, a couple of questions/notes that may effect the rest of your campaign:
ASI:
There's normally an optional rule to swap out ASI for feats if the player wants to, is that allowed?
Ammunition:
Some groups tend to, at least partially, ignore how much ammo people with bows are actually carrying. Are you going to do this with your group? I don't believe gunpowder has a rulebook suggested cost so you'll have to figure that out, maybe just using arrow costs.
Weapons:
Your weapon list is likely referring to homebrew weapons, whilst some guns exist in the PHB the revolver does 2d8 which is overpowered for a normal starting weapon at range. I suggest reskinning a crossbow or something similar for all these suggested weapons. I have no idea what the grenades are meant to be in context.

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Overall the class isn't really in a reviewable state, some things referred to simply don't exist in the linked content, such as Skill Shots which are part of the gunslinger class linked above (though called "Trick Shots").

Here are a few notes if you want to continue your version however:
Wary:
Slightly weaker version of the alert feat, this is campaign dependent but will likely have a large effect on the campaign if it has any effect as it will in essence make the party un-surpriseable.

Grit/Skill Shot:
To much for level 1, this is an archetype ability (and also named differently in 2 places), this should be given at level 3, if you think the game would be to boring starting without such an ability simply start your campaign with characters at level 3.

Shooting Styles:
This is a slightly less variable version of Fighting Styles, take a peak at either Ranger who also get this at 2nd level if you want to give more options (Though places may list UA content too, which you probably shouldn't allow).

Gunsmithing:
Level 3 is usually your archetype which is a lot stronger than making a weapon, which may be a slow process and awkward to balance for a new DM. As stated before, this should probably be Skill Shots.

Extra Attack:
This is a holdover from its Fighter origins, make it 5th, 11th, and 20th.

Bullet Time:
This is a strong ability to give. Doing an average 48 damagebefore crits and if you use a reskinned crossbow as a your gun (This class will have 20 Dex by level 10). Classes normally get a semi decent thing for level 10, take champions for example:

Additional Fighting Style

At 10th level, you can choose a second option from the Fighting Style class feature.

Which can be reskinned for Shooting Styles.
That being said, a fighter can attack 4 times once per day at this point 1 level later they can do 6, and at level 20 they can do 8. So this would just be a worst fighter at high levels.

Answer 2

Broken

This would probably be the strongest level 1 class due to the gun attack dies, massive reserves of starting ammo, grenades, free alert, and skill shots (by the way, the rules for skill shots are missing).

What's more, extra attack progression almost on par with Fighter (lagging 2 levels behind at 11, but they get the 5th level EA which is the most important), and more ASIs than a Rogue (and better progression). Marksman is also fairly nuts.

How to fix the class? Tell your player to play a fighter and pick up the Gunner feat from Tasha's. If they want trick shots, take the Battle Master archetype. You do not need an entire homebrew class to do what a feat was already made for.