Ranged Battlemaster vs. Wyvern

 I like the flavor of Matt Mercer's Gunslinger subclass, which was famously used by Taliesin Jaffe in Critical Role's first campaign. But the downsides, mainly the chance at Misfire on your attacks, is a kind of class design that doesn't really fit with other 5E class and subclasses, with nearly all features being pure positives. It may have been a holdover from Pathfinder or 3.5, but it always bugged me that a non-Gunslinger in 5E could fire guns without worrying about their breaking while a Gunslinger did have that concern.

So, I have long thought that if I wanted to create a similar kind of character, I'd go Battlemaster. Indeed, the Battlemaster and Arcane Archer already have similar ideas to a Gunslinger, with a limited ability to alter shots, but I think the Battlemaster is the most versatile.

Now, ranged characters are a little nerfed in 5.5, thanks to the change to Sharpshooter. But I don't know that it's that terribly bad, especially when we consider a couple workarounds.

I see two primary paths here for damage, built around two specific feats: Crossbow Expert and Great Weapon Master.

Now, just to address the issue: this build probably won't work all that great with guns. The two firearms available in the PHB (formerly the "Renaissance era" firearms) hit hard, which is nice, but they have some major downsides. One is range - the Pistol only has a short range of 30 feet, and the Musket only 40. But the bigger one is that there's no feat in 5.5 that allows you to ignore their Loading property. While you could very easily just take the Gunner feat from Tasha's, if you're allowed to grab 5.0 material (which I generally assume,) this feat mostly just lets those weapons work rather than actually boosting their damage. Downgrading to a d8 from a d10 is not an enormous damage loss, and you get a lot in return.

Let's talk about what Crossbow Expert does for you: this is a feat that might play into the build in both of its iterations. The most crucial thing it does is let you ignore the Loading property, which would normally prevent the weapon from really being used with a class that uses Extra Attack. It also allows you to attack in melee without disadvantage if you're shooting a Crossbow, which is certainly nice. The last bit, and the one that may or may not actually be useful here, is that you can add your ability modifier to the bonus attack you get with the Light Property as long as the attack is made with a Hand Crossbow and you aren't already adding it (such as from the Two Weapon Fighting Style feat).

The latter piece basically enables you to dual-wield Hand Crossbows (like a Diablo III Demon Hunter) and even more or less gets you the Two Weapon Fighting Style as part of it to allow you to grab just Archery.

Now, even if we want to use a Heavy Crossbow, we'll want this feat anyway, so you could take it at level 4 and be a little freed up in terms of which option you want to use.

The other feat, Great Weapon Master, is more specific, and a little kludgy. While GWM boosts solely Strength and its Hew property only works on melee weapons, the Heavy Weapon Mastery aspect of it actually applies to two specific ranged weapons: the Longbow and the Heavy Crossbow. (Bizarrely, the Automatic Rifle, Shotgun, and Musket don't count).

Now, if we're dual-wielding Hand Crossbows, this won't do anything for us. That might be nice, as we could focus on Dex-based feats, but I also suspect this will be a bigger boost to our damage.

Just to figure that out before we go into other choices, let's figure it out really quick:

Fighters don't need their bonus action every round unless they're dual-wielding, so the two hand crossbows should be pretty easy to use most turns. With three feats by level 10, we could get our Dex to 20 (though we might be behind if we go with GWM). At this level, we could shoot three Hand Crossbow attacks per turn, each of which is adding Dex, so if we figure that's like 1d6+5 three times, that's 8.5x3, or 25.5 damage. If we are shooting a Heavy Crossbow twice, but getting to add our proficiency bonus because of GWM, even if our Dex is only +4 at this level, that's 1d10+8 twice, or 13.5x2, which is 27. It will be slightly less because of the fact that our hit chance is a little lower.

That said, Hand Crossbows have Vex, which is a more direct boost to damage than Heavy Crossbows' Push. Indeed, because we have Tactical Mastery at this level, both the Heavy Crossbow's Push and Longbow's Slow masteries are essentially worthless to us, as we'd be able to do that with any weapon.

Still, given that the scaling would favor the Heavy Crossbow at higher levels as both PB and our number of regular attacks go up, I'm going to go that way.

So, with that in mind, here's how I'd go with feats:

At level 1, our Fighting Style feat is of course going to be Archery, a very solid one, giving us +2 to hit with ranged attacks.

At level 4, I think we pick up Crossbow Expert. For the next two levels, we can freely swap between going Heavy Crossbow or two Hand Crossbows.

At level 6, we grab Great Weapon Master. We will need to have at least a 13 in Strength to grab this, but given that we're pretty single-ability-score-dependent, I don't think that'd be too taxing on our build. The main downside is that we won't cap Dex at level 8 unless we take a full ASI.

But, at level 8, I think we have a couple compelling options: Piercer is actually a pretty obvious choice - all ranged weapons save "futuristic" ones do piercing damage, so this should apply to basically everything we do, and we can even grab a rapier if we want and still benefit (though thanks to Crossbow Expert, we might as well still shoot our Crossbow).

Mage Slayer, of course, is always a good option as well.

I actually think I'm going to go with Mage Slayer, not because it's necessarily the best choice here, but because I don't want to have to worry about the once-per-turn reroll of damage.

As a note, if we prefer the aesthetic (or the very long range) of Longbows, we could swap out Crossbow Expert for Sharpshooter. Our damage takes a slight dip, but we will also be able to ignore cover and be fully effective at 600 feet (imagine being able to nail a foe at a length of two football fields - not that your DM is likely to put you in situations where you can actually do that).

Ok, that's feats and equipment sorted. Our final bit of set-up is Maneuvers.

We'll know seven maneuvers by level 10, and we have five d10 superiority dice.

Goading Attack is very nice on a ranged attack, as it might simply impose full disadvantage on the attack (though we can kind of get this by swapping in the Sap property).

Menacing Attack, imposing frightened at range, can literally stop a target in their tracks.

Pushing Attack might seem redundant with the Push Mastery, but consider that you can add both, potentially pushing a target away up to 25 feet.

Maneuvering Attack can help you play a kind of overwatch role, helping allies get into position or away from danger.

Commander's Strike might not be quite as exciting given that we're going to be hitting quite hard on our own, but it can massively improve the damage of a Rogue by giving them potentially a second Sneak Attack per round.

Precision Attack is not quite as important with the new Sharpshooter, but it will help prevent misses. Given that we'll have a pretty high attack bonus, I doubt we'll be using this a ton, but it can keep our damage consistent.

Honestly, I think this is going to rely a lot on your party makeup. But the key is that we can probably afford to use a maneuver on most turns, though we'll burn through them pretty quickly if we try to use them on every attack.

Let's assume the following:

If we land a critical hit, we'll burn a Superiority Die to get some extra damage. For the sake of our damage calculations, we'll assume we're not burning maneuvers outside of that scenario. This will deflate our damage output a bit, but one of the things that's really appealing about the Battle Master is that they don't necessarily just have a pre-programmed "rotation," and can be very reactive to the situation on the battlefield.

So, each turn, we attack twice. We'll burn a maneuver on a crit, meaning we might do that twice in a turn where we get very lucky and crit twice. We can say, just for the sake of consistency, that it's a Menacing Attack, or a Pushing Attack if they're already frightened of us.

If we do miss, we'll burn a die to try to hit with a Precision Attack.

Let's math it out:

We have a +4 to Dexterity, so with the Archery Fighting Style, our attack bonus is +10. Thus, we hit on a roll of 4 or higher. And if we roll a 2 or 3 (nat 1 is still an auto-miss) we can do a Precision Attack (we don't miss out on the Menacing/Pushing damage because we're already not critting). If we had rolled a 3 on the die, this will always turn it into a hit. If we had a 2, it's a 9/10 chance that it also turns it into a hit, so basically, within that 10% of rolling a 2 or 3, 95% of the time, it's still hit. So, that's 85% plus 9.5%, meaning we effectively have a 94.5% chance to hit. Our crit chance is the same standard 5%.

Our hit damage is 1d10+8, or 13.5 on average (the extra 4 coming from Great Weapon Master). However, our crit damage bonus is effectively 3d10 if we're saving maneuvers for crits, so that's 16.5.

Thus, we're looking at 13.5x94.5% or approximately 12.76, plus 16.5x5%, or .825, giving us 13.585 damage per attack. This then doubles with our two attacks to 27.17.

That's actually pretty low compared with some of the other things we've been doing. But let's assess some other elements:

First off, we'll probably do a little more damage because we might not save all our superiority dice for near-misses and crits. Also, the utility of inflicting the frightened condition can be pretty huge (or DC would be 16, which is decent). Against flyers, Trip Attack can actually be really powerful if they don't have Hover.

Also, this damage goes up by a full 50% at the next level, where it starts to look a lot more respectable.

I think the takeaway here is that you shouldn't expect to be the real damage-dealing powerhouse of the party. Instead, you've got a ton of utility you can apply while still making a meaningful contribution to the party's damage.