Never tried homebrew but I had an idea. I've seen in movies and shows how shooting someone at point-blank is basically guaranteed, or as close to guaranteed as you could feasibly get. So, I was thinking of an idea of something implementing that into D&D (Yes I know about the disadvantage on ranged attacks in melee distance but hear me out). For certain weapons and spells (guns but not bows, Eldritch Blast but not Sacred Flame, etc.), if a player could get within melee distance on an enemy you could go for a point-blank attack, where the target can make a DEX saving throw (w/o disadvantage), and if they fail the attacker gets a bonus (either advantage or a bonus to the attack roll). I figured making the attack guaranteed would be broken and not totally realistic (a point-blank shot on armor would still have some chance to mitigate the attack). This isn't well structured, I'm new to this stuff, not even considered attack roll spells vs saving throw spells and other stuff, but I would like to know what others think about it, just get some discussion going.

This was sort of a thing in d&d: https://www.d20srd.org/srd/feats.htm#pointBlankShot

Of course, since that was 3rd edition, the feat didn't have much to it. Point Blank Shots involve the sacrificing the advantage of range, what I would give in recompense for this sacrifice is that it deals additional damage or critically hits more likely. Being within 5 feet, it already gains advantage if the target has the prone condition, and there's not much you can do in 5th edition to increase accuracy further without going outside the intended design or being cumbersome.

I would, however, suggest making this option as part of a Feat, and not something just anyone can do. Roughly, I would make the Feat have the following benefits:

• Increase your Dexterity or your Spellcasting Ability Score by 1.
• You no longer suffer Disadvantage for attacking with a firearm or a ranged Spell Attack, while in an enemy's reach.
• If you successfully hit a target within 5 feet of you with a damaging Firearm Attack or ranged Spell Attack, you deal 1 additional die of that damage. You can only benefit from this additional die once per turn. This additional die of damage is doubled like other damage if you critically hit.

Well, that's something I never knew. That is kind of cool that someone did try it at one point. Making it a Feat would make sense since would be useful for both Gunslinger fighters and Melee casters. Not sure about balance, since I don't know jack about that. But I am imagining some cool gun kata stuff that could be done with it, or a Warlock Eldritch Blasting someone in the face.

The issue with your idea is how much it will bog down combat. If every target has to make a Dex save before you can even attack them… that’s a lot of extra rolling. As a DM, I would be very dubious about allowing this at the table because combat already bogs down a lot as it is.

Right. I'd go with either an autohit with a DEX SAVE -or- regular 'to hit' attack mechanics with no disadvantage, not both.  I would grant an additional die of damage. *I already homebrew CRITS with max damage die so the pointblank damage is differentiated.

Quote from Shadowfire1500 >>

For certain weapons and spells (guns but not bows, Eldritch Blast but not Sacred Flame, etc.), if a player could get within melee distance on an enemy you could go for a point-blank attack

 Generally when you want to scope the feature to certain weapons or attacks, you might want to consider methods that apply only to those things. A gun enchantment, for instance. Or if you're making some kind of gun kata monk subclass, just make it a feature of the subclass. It's a bit easier to guard against abuse/unintended consequences of a feature when you limit the reach of that feature.

And there would be unintended consequences here. Ranged builds are supposed to play different from melee builds. They benefit by attacking at range, but the tradeoff is that they are less effective when you close the gap with them. Without that, ranged weapons are just objectively better. Similarly, allowing Eldritch Blast to be even better in melee range would easily outclass any other melee option for warlocks.

Honestly, you all make good points. This idea was just a random thought I had, so it is cool to see more experienced players and DMs show how they see the ups and downs of such ideas. Thanks for the comments. 

I think the easiest way to keep this simple is to just leave it up to the existing rules; a DM always has the power to grant advantage or disadvantage beyond what a character has by default, so they could simply grant you advantage for a shot that they agree is easy for some reason that the rules don't normally provide for?

But it shouldn't simply be ranged based; keep in mind that if an enemy is aware of you then they will be trying to avoid getting hit, and that's part of what the attack roll and Armor Class represents. The closer you are, the less time your enemy has to react, but the same is also true of you, and you need to adjust by a greater amount to keep your aim (at a long distance you're adjust by fractions of a degree, rather than multiple degrees at close range); while in practical terms being closer may still be easier, I think it's borderline enough it's simpler just to ignore it most of the time.

However, if you're in a firing line waiting to fire a volley once the enemy draws closer, then advantage may make sense as you're delaying for an easier shot.