I am theorycrafting a level 10 character. (If my math here checks out, there is actually a better build I could do for it at higher levels.) In this build we’ll be taking 5 levels in Ranger and selecting the Hunter subclass, with the Horde Breaker feature chosen at level 3. This feature reads as follows:
Once on each of your turns when you make a weapon attack, you can make another attack with the same weapon against a different creature that is within 5 feet of the original target and within range of your weapon.
Now from what I’ve checked of the fighter, the subclass you pick for it doesn’t matter all that much, and since none of them seem to really effect the maths I’m working with, we’ll just say it’s a Battle Master, since that’s likely what I’d pick myself in the long run.
At level 5, rangers get their Extra Attack feature. By level 5, fighters have both their Action Surge (level 2) and first Extra Attack (level 5) features. Action Surge allows you to take another action once during your turn, regaining the ability to do so after a short or long rest.
Now if I am correct, Action Surge also allows for your extra attacks to be used if you take the Attack action with your extra action. (It may well also make it possible to retake a bonus action activated by any feats based on Attack actions, but I don’t believe this to be the case.)
The Crossbow Expert feat (PHB, p. 165) has 3 benefits, two of which are going to be a part of this calculation. The first is that you ignore the “loading” property of any crossbow you are proficient in (the Light Crossbow is a simple weapon, while the Hand Crossbow and Heavy Crossbow are martial weapons; bear this in mind when picking classes/backgrounds). The second relevant feature is written as follows:
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.
Given all the previous information, I believe the following turn I am about to post is possible, provided you target an enemy that has another enemy within 5 feet of it. It is also important to mention that due to the rules behind ammunition, you will require both enough ammunition available for this and one hand free to reload your weapon:
- Attack, Extra Attack, Extra Attack, Horde Breaker attack (I believe this can be taken at any point during your attacks, though I may be incorrect), bonus-action attack (via Crossbow Expert), attack (via Action Surge), Extra Attack, Extra Attack
This by my count is 8 attacks in a single turn, accomplishable once between every short or long rest. Assuming the use of the hand crossbow (as I am not sure how the light and heavy crossbows would work in regards to having one hand free to reload, although I imagine that depending on DM ruling it would be possible with them) this results in 8d6 piercing damage in a single turn at level 10 as a martial with only the Crossbow Expert feat.
This is likely not a majorly impressive feat and I’m sure it’s possible to get more damage out with far less “faffing around” as it were, and I believe you can get much more out of it via the Sharpshooter Feat, but I am interested to see if my math checks out here.
I’m also interested to know whether you’d get a second bonus attack via Crossbow Expert as part of your attack action via Action Surge, as the feat itself does say, “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.”
What is the maximum number of attacks I can make with this character in one turn, using Action Surge?