Can I make a melee attack with a ranged weapon?

Question

Are there any rules that preclude this action?

I know weapons with the Ammunition property are treated as improvised weapons per this line and this question:

If you use a weapon that has the ammunition property to make a melee attack, you treat the weapon as an improvised weapon .

... but what about darts and nets? Am I forced to use them as an improvised weapon to make this melee attack or can I simply make an attack with the ranged weapon (including any properties therein)?

Keep in mind, I am almost certain this isn't the intended result, but what is RAW?

Answer 1

Only as an improvised weapon.

From the description of improvised weapons in the rules (PHB, p. 147-148):

Sometimes characters don’t have their weapons and have to attack with whatever is close at hand. An improvised weapon includes any object you can wield in one or two hands, such as broken glass, a table leg, a frying pan, a wagon wheel, or a dead goblin.

In many cases, an improvised weapon is similar to an actual weapon and can be treated as such. For example, a table leg is akin to a club. At the DM’s option, a character proficient with a weapon can use a similar object as if it were that weapon and use his or her proficiency bonus.

An object that bears no resemblance to a weapon deals 1d4 damage (the DM assigns a damage type appropriate to the object). If a character uses a ranged weapon to make a melee attack, or throws a melee weapon that does not have the thrown property, it also deals 1d4 damage. An improvised thrown weapon has a normal range of 20 feet and a long range of 60 feet.

Rules designer Jeremy Crawford unofficially confirms this ruling on Twitter:

Can a Barb/Fighter use a Dart in melee (w/STR) to benefit from Rage and Archery Fighting Style? Ranged weapon, melee attack

If you use a weapon in a way contrary to its design (melee attack w/ a ranged weapon), see "Improvised Weapons" (PH, 147). DM's call.

Improvised dagger then? In accordance with the rules on that page?

If you turn the page, you'll see the standard thing to do with a ranged weapon being used as a melee weapon.

It seems clear that the intent is that any usage of a ranged weapon to make a melee attack (i.e. hitting them with the weapon itself) would involve your ranged weapon being treated as an improvised melee weapon, so the attack would follow the rules for improvised weapons. While the DM could house-rule otherwise, this is how such situations are handled by the rules.

Answer 2

Treat as Improvised Weapons

Using a ranged weapon as a Melee weapon activates the Improvised Weapons rules (emphasis mine):

If a character uses a ranged weapon to make a melee attack, or throws a melee weapon that does not have the thrown property, it also* deals 1d4 damage. (PHB p. 147)

Because it's purely improvised, it wouldn't utilize any of the other properties of the actual item (such as the Net's Restrained condition.)

*This is referring to the earlier sentence, equating the damage a ranged weapon used in melee to an object that has no resemblance to a weapon:

An object that bears no resemblance to a weapon deals 1d4 damage.

Is it a melee weapon or a ranged weapon?

The weapons table (PHB, 149) lists which weapons or Melee vs Ranged. Some melee weapons have a Thrown property which allows them to be used as Ranged weapons, but no Ranged weapons have a property that allows them to be used a Melee weapons. If it doesn't doesn't state you can use as both, then whatever isn't listed becomes an improvised weapon attack. This is from the Weapons description on page 146 (emphasis mine):

Every weapon is classified as either melee or ranged. A melee weapon is used to attack a target within 5 feet of you, whereas a ranged weapon is used to attack a target at a distance.

The absence of a mechanic for allowing a Ranged Weapon to be used in Melee turns the use of that weapon into an Improvised Weapon.

Mechanic for using Ranged while within Melee

There does exist a mechanic for using a ranged weapon in Melee range: Disadvantage. See Page 195 of the PHB for Ranged Attacks in Close Combat:

Aiming a ranged attack is more difficult when a foe is next to you. When you make a ranged attack with a weapon, a spell, or some other means, you have disadvantage on the attack roll if you are within 5 feet of a hostile creature who can see you and who isn’t incapacitated.

This is supported by Jeremy Crawford

On twitter, he stated

If you use a weapon in a way that turns it into an improvised weapon—such as smacking someone with a bow—that weapon has none of its regular properties, unless the DM rules otherwise.

Answer 3

You can use ranged weapons to make melee attacks but only as improvised weapons

Using ranged weapons to make melee attacks is explicitly allowed in the rules. In the section of the PHB entitled "Improvised weapons" it describes the rules you use when attacking in this way:

If a character uses a ranged weapon to make a melee attack, or throws a melee weapon that does not have the thrown property, it also deals 1d4 damage. (PHB p. 147)

Improvised weapon or not?

The rules above say that the damage dice of a ranged weapon used to make a melee attack changes to a d4 as opposed to its original damage die. However, it never unambiguously explicitly says that when used in this way they are considered improvised weapons. Some may argue that it is implied by virtue of them being under the "Improvised Weapons" section, but this is not explicit (though it seems like a very reasonable interpretation).

However, Jeremy Crawford has cleared up this potential ambiguity on Twitter:

If you use a weapon in a way that turns it into an improvised weapon—such as smacking someone with a bow—that weapon has none of its regular properties, unless the DM rules otherwise.

So using a bow (a ranged weapon) to make a melee attack will turn it into an improvised weapon. Thus, according to Jeremy Crawford, it appears that the excerpt from the PHB above is indeed supposed to be read as turning those weapons into improvised weapons despite not being explicitly stated.

Thus, using a net or a dart (both ranged weapons) to make a melee attack will turn them into an improvised weapons for that attack.

Also, note that this means that the improvised weapons will have none of the properties the weapons have when used properly. Which means the net won't restrain for example.