Twin hand crossbow Fighter: is this build valid?

Question

The Sharpshooter feat includes an interesting feature: you can choose to take -5 penalty to hit with a ranged weapon attack to increase its damage by 10. Normally, I'd dismiss the trade-off as too situational, but I've only just thought of combining it with the Archery fighting style (+2 to hit with ranged weapon attacks).

After building a sample character using these features, the end result looks quite effective. My questions are: Is this build valid? Have I interpreted the rules correctly? If so, how well does it compare against other damage-focused builds?

5th level variant Human Fighter:

• Ability Scores (via point buy): Str 10, Dex 16, Con 16, Int 9, Wis 12, Cha 10
• HP: 47, AC: 17 (or 18 with disadvantage on Stealth)
• Weapons: Hand Crossbow x 2
• Fighting Style: Archery
• Martial Archetype: Battle Master (with the Precision Attack maneuver)
• Feat (variant Human): Crossbow Expert
• Feat (4th level ability score improvement): Sharpshooter

The end result is a fighter capable of hitting targets 120' away, behind 1/2 or 3/4 cover, or engaged in melee with him, all without penalty. Normally, he can make 3 such attacks per round (Attack action + Extra Attack + Crossbow Expert's bonus attack). Once per short rest he can make 5 attacks per round via Action Surge (Attack action 1 + Extra Attack, Attack action 2 + Extra Attack, Crossbow Expert's bonus attack).

His normal attack bonus is +8 (3 proficiency, 3 Dexterity, 2 Archery fighting style), and normal damage is 1d6+3. Not amazing damage, but nice accuracy and flexibility (attacks can be focused on one target, or spread around; works equally well in melee and ranged combat).

The real winner is his ability to take -5 on any of these attack rolls to increase the damage by 10, to an average of 16.5 per shot (excluding crits). If he lands his usual 3 attacks, that's ~47 damage; 5 attacks is ~83. While the -5 to hit seems imposing, he's still got superiority dice: he can increase his attack roll by 1d8 after seeing the result, up to 4 times per short rest. And even without the superiority dice, his attack bonus is still an acceptable +3; ok for hitting low AC targets, or those granting advantage on attack rolls (e.g. surprised or prone + adjacent).

With a decent AC, a Fighter's HP, and the Second Wind feature, he can also take a decent amount of damage. He'll also have decent Strength, Dexterity, and Constitution saving throws.

This build seems almost too well rounded. Unlike a blaster, he only requires short rests to recover his big hitters. Unlike a brawler, he can target just about anything on the field at a moment's notice. Have I missed any rules, or overlooked any drawbacks?

Answer 1

Yes, this build works, and it is strong.

I ran the numbers, and the average damage using your build and the -5/+10 feature gives you an average at level 5 of 22.8 damage per round (dpr). By comparison, a Great Weapon Fighter build with either the Great Weapon Master or Polearm Master feat deals an average of 18.7 damage at the same level. This build maintains a significant lead over those builds all the way up to level 20, for a total of 42.5 dpr at level 20 compared to GWM's 34.3 dpr.

However, the real difference between the builds is how the weapons work. Your crossbow build has the benefit of range, but the other builds get their own benefits. A Polearm Master has incredible control over the battlefield with their increased reach and many possible opportunity attacks, and a Great Weapon Master can deal much more damage if they get the chance to cleave through enemies and/or use opportunity attacks.

Compared to a caster, you'll probably beat them in raw damage, but casters can do a lot more than deal damage, so that's not saying much.

Answer 2

There's a flaw with this build - You require a free hand to load a crossbow.

From the PHB Errata:

Ammunition (p. 146).
Loading a onehanded weapon requires a free hand.

Answer 3

Yes, It works. And you don't need two crossbows, as it is enough to have one. As we look on crossbow expert:

Source: Player's Handbook

Thanks to extensive practice with the crossbow, you gain the following benefits:

• You ignore the loading quality of crossbows with which you are proficient.
• Being within 5 feet of a hostile creature doesn’t impose disadvantage on your ranged attack rolls.
• When you use the Attack action and attack with a one handed weapon, you can use a bonus action to attack with a hand crossbow you are holding.

If you wield one-handed weapon. It doesn't say other weapon. So you can hold Hand crossbow, shoot, reload as you have free hand and shoot again as bonus action. Nice for rogue for example.