The Joy of Guns – Part 2

In the last article we made some design decisions about firearms and used muzzle energy and medical articles to categorize different weapons into groups.

Guns guns guns...

You can read all of that by following the link below:

We’re going to carry that work forward as we develop our rules for the new weapons.

Weapon Accuracy


A Riding Gun Fight

D&D provides the character a proficiency bonus for using weapons.  The proficiency bonuses scale from +1 to +3.  Other bonuses from feats, item properties, and magic can also increase the accuracy of your weapon.  With that in mind I’m creating a guideline for setting a ballistic weapon’s proficiency bonus:

Proficiency Bonus Modifiers

  • Handgun: +1 bonus
  • Long gun: +2 bonus
  • Smoothbore barrel: +0 bonus
  • Rifled barrel: +1 bonus
  • Shotgun: +0 bonus
  • Scopes: provide an item bonus to attacks (+1, +2, etc.)


The Musketeer carries a long gun with a smooth-bore barrel for a +2 proficiency bonus

You can use these as cumulative modifiers to find a total proficiency bonus.  Here is a breakdown of proficiency bonuses calculated for a few example guns.

Example Gun Proficiency Bonuses

  • flintlock pistol = handgun, smoothbore  = +1
  • flintlock musket = long gun, smoothbore = +2
  • modern handgun = handgun, rifled = +2
  • modern rifle = longarm, rifled = +3
  • modern scoped rifle = long gun, rifled, scope (item bonus) = +4
  • Blunderbuss = shotgun, long gun, smoothbore = +2
  • Dragon (blunderbuss pistol) = shotgun, handgun, smoothbore = +1


A long gun with a rifled barrel provides a +3 proficiency bonus

Most of that will be invisible to the player who merely selects the gun and writes down the bonus just as he would for a dagger or longsword, but it provides someone wanting to bring their favorite gun into the game an easy tool for setting the proficiency bonus.

Weapon Damage


Gunshot wound to the neck

We have already broken guns into three categories:

Low-Powered Ballistic Weapons

These are early firearms like Flintlocks and low energy modern hand guns like the .38 police special.  One shot from this weapon drops a minion but other monsters may keep going.

Key characteristics:

  • Weapon Type: Ranged
  • Weapon Group: Ballistic
  • Attack: DEX vs. AC
  • 2 damage dice
  • Property: High Critical

Mid-Powered Ballistic Weapons

This includes high-powered handguns, possibly early long guns like muskets, and low powered rifles.  These should ignore armor and do more damage.

Key characteristics:

  • Weapon Type: Ranged
  • Weapon Group: Ballistic
  • Attack: DEX vs. Reflex
  • 3 damage dice
  • Property: High Critical

High-Powered Ballistic Weapons

Our final category includes very powerful handguns, rifles, and assault weapons.  These weapons will often send bullets completely through the target and can cause cavitation (nasty large exit wounds).  Remember that D&D heroes are mythically endowed with the ability to survive real-world damage so we aren’t trying to guarantee a kill.

Key characteristics:

  • Weapon Type: Ranged
  • Weapon Group: Ballistic
  • Attack: DEX vs. Reflex
  • 4 damage dice
  • Property: High Critical

Next, on page 220 of the Fourth Edition Player’s Handbook the rules describe damage increases for one-handed and two-handed weapons as they increase in size.   These damage progressions look like this:


1d4 –> 1d6 –> 1d8 –> 1d10 –> 1d12 –> 2d6 –> 2d8 –> 2d10


1d8 –> 2d4 –> 1d10 –> 1d12 –> 2d6 –> 2d8 –> 2d10

The idea of scaling melee weapon damage by size provides us a conceptual guideline for scaling firearm damage by muzzle energy.  Creating our damage progression is a bit of a subjective and  artistic process.  It needs to remain somewhat balanced while still “feeling” about right.  Looking over the damage produced by different magic items in the Player’s Handbook, some of these (like vicious weapons) pack a pretty hefty punch which tells me that as long as I provide item levels as guidance for the DM I am not breaking the game.

More powerful guns shouldn't break the game

Here then is my proposed firearm damage progression color coded to indicate Low-Powered, Mid-Powered, and High-Powered weapons.

Firearm Damage Progression

2d4 –> 2d6 –> 3d4 –> 3d6 –> 3d8 –> 4d6 –> 4d8 –> 4d10

Next we need to tie these damage dice to muzzle energies.

  • No damage = less than 100 foot-pounds
  • 2d4 = 100-299 foot-pounds or less
  • 2d6 = 300 – 499 foot-pounds
  • 3d4 = 500 – 649 foot-pounds
  • 3d6 = 650 – 799 foot-pounds
  • 3d8 = 800 – 999 foot-pounds
  • 4d6 = 1,000 – 1,999 foot-pounds
  • 4d8 = 2,000 – 5,000 foot-pounds
  • 4d10 = greater than 5,000 foot-pounds

This guideline lets us choose any weapon (with an ammunition type), calculate the muzzle energy, and then find the damage.  Most guns will list muzzle energy on Wikipedia if you select the ammunition.  You can also use any of the muzzle energy calculators on the Internet to find muzzle energy for older firearms by using muzzle velocity, weight, and diameter of the projectile.

Here are some muzzle energy calculators you can use:

What’s Next?

We still need to handle rate of fire and a bit more before we can start statting out guns.  In addition, we should consider gun feats, grenades, explosives, and, of course, cannons.

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