I can't believe they went that way with hand crossbows.
You are right. And you don't have to respond to me if you want me to go away. But until then, I have to refute your points.
Really?!?!
In your experience, hand-crossbows are effective at parrying melee weapons?
A momentary threat provides defense for an entire 6-seconds or so of combat?
So after they shoot, how are they defending them self with their sword in it's sheath?
Exactly. Standing toe to toe with an opponent that is actively attacking them with a melee weapon. Taking the time to sheathe a weapon, namely the weapon one is using to fend off the melee attacks of your opponent, is a very bad thing.
For me it's a case of using the rules, not letting the rules use you. The reality of combat is that a hand crossbow is a momentary threat which once fired is no longer a danger. Even if the Crossbow Expert Feat allows a reload quick enough that it doesn't affect your action economy, it still does take time, even if just a millisecond; time that an opponent engaged in melee combat can exploit.
Nobody would ever do this in real-life because to do so would mean death. Therefore that's not how it's done in my games.
By RAW, you are right. But my post wasn't about RAW, it was about my ruling based on what I see as RAI. In my games, unless one is specifically trained in unarmed combat against armed foes, such as a Monk, one cannot defend them self in melee combat without a melee weapon - thus, they provoke an attack of opportunity for dropping or stowing their weapon and not disengaging.
The reason why a disengage action exists is two-fold: one, the game needed a mechanic for someone to move away from an opponent without provoking an attack of opportunity, one balanced by the expenditure of an action economy resource; and two, the conceit is that a combat round consists of a constant trading of blows, parries, and feints - not just one single attack. Because of this conceit, I see the Rules as Intended to mean that one cannot drop their defenses during melee combat unless one actively disengages from that combat.
Yes, they are trained in that manner, and receive a specific benefit: they don't suffer disadvantage for the shot. That's it. No amount of training can make a hand-crossbow something it is not; specifically, a melee weapon able to defend one in melee combat. I see their training as primarily focused on fast, precise loading, and secondarily as being experienced at snapping off a shot during melee; but that doesn't make them immune from the need to continuously defend themselves through the entire round.
What kerleth posted may be RAW, though I didn't evaluate it in the context of RAW so I'm not sure; but it certainly is not consistent with real combat, and I believe counter to Rules as Intended.
You can actually do this easier by simply dropping the rapier and then picking it up as a free object interaction.
It looks dumb, but it works. I personally allow characters to use their free object interaction to hold their weapon under their arm or in their shield hand, etc, so as to free up a hand for spellcasting or reloading ammo provided they aren't accomplishing anything they couldn't accomplish by dropping the weapon and picking it back up. Since the rules allow you to drop and scoop it up, I just allow them to mechanically mimic that while maintaining control over the visualizations.
I'm sure that an expert xbow user could load a small xbow with 1 hand while holding something in the other. slip the bow between the knees cock it and slide in the bolt. Presto! granted realism is out the window in terms of melee combat, but not unreasonable if they are at range.
I understand where you're coming from, especially with reference to realism, but if it was intended that holding a melee weapon made you less vulnerable to the blows of an enemy due to the added ability to parry, then I would expect such weapons to give you an AC bonus. Since they don't, I would think that the intention is that the entire issue be disregarded.
The other way to enforce this, which just occurred to me, is if you shoot the crossbow as your bonus action and then decide, for whatever reason, not to attack with the one-handed weapon, then the crossbow attack is no longer a bonus action, but qualifies as your action instead.
A crossbow has a higher draw weight than a longbow. That is why you can draw the longbow with one hand. A crossbow is designed to let you put much more force in the bolt, by holding the draw mechanically. That is why bolts penetrate better than arrows. It was this power that had the crossbow declared as the ultimate weapon when it was introduced in Europe (it was already in use in the Orient years before).
However, with the high draw strength, it is very difficult to draw one handed (unless you don't care about your back). You can use a crank one handed but it takes longer, and it still needs to be braced.
However, this is a fantasy game. Real middle age bowmen did not have the skills of those in the game. There were no Legolas' running around. Most of the bowmen were the worst trained of the soldiers, and would usually be slaughtered once the enemy broke the lines. Most of the time they fired in the air in an arc as a group on the hopes that some will accidentally hit the enemy. So the real weapons are not a good model when emulating high fantasy fiction.
As for "slipping it between the knees," crossbows had a bracket on the front end to put your foot in while you pulled the string back with both arms . Essentially you are using two arms and a leg to reload it. So you should not be able to move or have a free hand for melee. And your defense is compromised because it is hard to dodge while loading. An unnaturally high strength might be able to overcome the problem.
As DM, if you were to sheathe your melee weapon while engaged in melee combat (in a situation that would require you to take the Disengage Action to avoid an Opportunity Attack), my ruling would be that you trigger an Opportunity Attack.
As a certain Dark Lord of the Sith once said: You are unwise to lower your defenses.
In your example above, if you are moving from target to target to make your melee attacks, you haven't accounted for taking Disengage Actions (or the movement).
The Crossbow Expert Feat eliminates disadvantage for making a ranged attack within 5 feet of a hostile creature.
It does not eliminate the need for Disengaging, or make you immune to Opportunity Attacks.
I think that the Rules as Intended mean that when in melee combat, you have to actively maintain your melee engagement or use the Disengage Action to leave your threatened square. As long as you are in that threatened square your opponent is attacking. You can't just sheathe your weapon while somebody is in your face attacking you with a melee weapon; at least if you don't want to give them a free shot at you that is.
The Lucky thing is one place where I'll be ignoring Sage Advice. That ruling falls under the heading of "Crawford brain fart" as far as I'm concerned--seriously, I have no idea what he was thinking. You can improve your chance to hit by closing your eyes? Riiiight.
(Edited after reviewing how Lucky works) I'm sticking with my previous ruling: You make the original roll with disadvantage, per normal. Discard the better die and keep the worse. Then you decide whether to use a luck roll. If you use a luck roll, you have your choice of using the new roll from Lucky, or the result of your roll-with-disadvantage. You don't get to go back, find the discarded result from the first roll, and fish it out of the trash. It's gone.
Everything else looks good though. Glad to see that we can quit talking about the dual hand crossbow/Sharpshooter build.