Firearms (5e Variant Rule)

A collection of variant rules useful for modern and futuristic firearms.

Armor Piercing

Attacks with weapons or ammunition with the armor piercing property are quite effective against armor. Armor Piercing always overlaps with Armor Piercing of a lesser numerical value - for example, an Armor Piercing 2 weapon is also Armor Piercing 1, and as usual when effects of the same name overlap, the more powerful one applies. Armor Piercing X always counts as an effect of the same name with itself, so values on the weapon and ammunition overlap rather than stack.

Armor Piercing (1). +1 to hit against targets with natural armor or worn armor and an AC of 14 or better.

Armor Piercing (2). +2 to hit against targets with natural armor or worn armor and an AC of 16 or better.

Armor Piercing (3). +3 to hit against targets with natural armor or worn armor and an AC of 18 or better.

Because you generally do not know the AC of your target, express a hit roll with, say, an Armor Piercing 2 weapon to your target of, say, 18 as "18 to hit, Armor Piercing 2".

Design Note

When designing weapons or ammunition, do not use the armor piercing property for attacks that would entirely ignore armor. Such a weapon would not use an attack roll at all: instead the target(s) would make some form of saving throw.

Burst Fire Nonproficiency

The DC of Dexterity saving throws made against firearms using burst fire (DMG p. 267) is 10 if the attacker does not have proficiency with the weapon.

Burst Fire Proficiency

The DC of Dexterity saving throws made against firearms using burst fire (DMG p. 267) is 13 + the attacker's proficiency bonus if the attacker has proficiency with the weapon. You may use this rule in conjunction with the Burst Fire Nonproficiency rule, above.

Hearing Distance

Firearms are very noisy! The following table gauges how difficult it is to hear a gunshot or explosion, by the size of a weapon. There are four brackets, each of which determine the DC of a hearing-based Perception check to hear a gun being fired. The first bracket ("Automatic") is the maximum distance within which a weapon is so loud, it's impossible not to hear it unless you are deafened. Within that radius, you do not have to make a Perception check to hear it; it is automatically audible. Further away, it is increasingly less certain; the next three columns give a DC which must be passed to hear the sound of a firearm.

Weapon Type	Automatic	DC 10	DC 15	DC 20
Suppressed or "Silent" Firearm	60 feet	120 feet	240 feet	480 feet
Light Pistol, Musket	200 feet	400 feet	800 feet	1,600 feet
Grenade Launcher1, Heavy Pistol	400 feet	800 feet	1,600 feet	3,200 feet
Rifle, Shotgun, Submachine Gun	800 feet	1,600 feet	3,200 feet	10.5 ¼ miles
Machine Gun, Stun (Nonlethal) Grenade	1,600 feet	3,200 feet	10.5 ¼ miles	20.5 ½ miles
Anti-Personnel Explosion, Grenade	3,200 feet	10.5 ¼ miles	20.5 ½ miles	5 miles
Anti-Vehicle Explosion, Tank Cannon	10.5 ¼ miles	20.5 ½ miles	5 miles	10 miles

¹This is the sound of a grenade launcher firing, not the sound of an exploding grenade, which is much louder (see further below on the table).

The DC of the Perception check assumes that the firearm is being used in a typical, relatively clear outdoors environment; the DC may be slightly lower when you are surrounded by stone or concrete (since those materials reflect sound, making it louder), or even lower in an enclosed space such as inside a building. On the other hand, the DC may be slightly higher in an environment such as a dense forest where there are many obstacles to diffuse the noise. Use common sense; it may be difficult to hear the sound of a pistol going off, even within the normally "automatic" distance (necessitating a Perception check), if there is a very loud background noise, such as heavy machinery or fireworks.

Short Burst

Firearms with the short burst property can, fire a number of rounds of ammunition with a single pull of the trigger. This is typically a three-round burst but could be anywhere between two and five.

When you make an attack with a firearm with this property, you can choose to expend a single round of ammunition as normal, or fire a short burst and expend additional rounds of ammunition as indicated in the parenthesis. If you fire a short burst and successfully hit, you can re-roll a number of the damage die, as indicated in the parenthesis, accepting the new results.

For example, a bolter has a short burst (2), so when you attack you expend three rounds of ammunition and can re-roll two of the damage die if you successfully hit.

Scope

Firearms with the scope property have a scope which facilitates extreme long-range engagements.

If you have not moved since the end of your last turn, you can use an action to aim down the scope of a firearm that has this property at a specific target. Once you do so, you are incapacitated and your speed becomes 0 until the start of your next turn. However, the first attack you make against the target at the start of your next turn is made as if the firearm has a different range value (listed in parentheses), with no long range at which attacking imposes disadvantage on your attack roll.

Misfire

Firearms with the misfire property jam regularly, or at the very least are very difficult to clear after jamming.

When an attack roll using the firearm is lower than the number listed in the parenthesis of the weapon's misfire property, it jams. While jammed, the weapon acts as an improvised weapon, rather than by its stat block. A creature proficient in the weapon may clear it as an action, causing the weapon to act as normal again.

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