Basic Submachine Gun

Martial Ranged Weapon (firearm), uncommon (DM may change rarity)

Stats

• Damage (Semi Auto): 1d8 piercing
• Damage Type: Piercing
• Range: 80/240 ft (short/long)
• Weight: 7 lb
• Magazine: 30 rounds
• Properties: Ammunition, two-handed, reload (30), special (modes below)
• Cost: 600 gp (weapon) Ammo: 30‑round magazine 1 gp; single bullets 0.05 gp each (30 bullets = 1.5 gp if sold loose)

Firing Modes (use one mode when you take the Attack action with the weapon)

Semi Auto (default)

• Make a normal ranged weapon attack: +proficiency + Dex modifier to hit.
• Damage on hit: 1d8 piercing.
• Uses 1 round from the magazine.

3 Round Burst

• As part of the Attack action, you can fire a 3-round burst. You make one attack roll at disadvantage.
• If it hits, the target takes 2d8 piercing damage (representing 3 close-grouped bullets).
• Uses 3 rounds from the magazine.
• Jam check: If the attack roll is a natural 1 while using Burst, the weapon jams. See Jam rules below.

Full Auto Suppressive Fire

• As an action, you may fire up to 10 rounds in a continuous stream. Pick the number of rounds you expend (minimum 2). You make a single attack roll with disadvantage.
• On a hit, the target takes 1d8 piercing + 1d6 piercing per additional 2 rounds expended beyond the first (round down).
  • Example: expend 6 rounds → base 1d8 + extra from (6 − 1) = 5 rounds → floor(5/2)=2 → add 2d6.
• Uses the chosen number of rounds from the magazine.
• Recoil check: If you fired more than 3 rounds, you must succeed on a Constitution saving throw (DC 12) or have disadvantage on attacks until the end of your next turn (difficulty scales with number of rounds at DM discretion).
• Jam check: If the attack roll is a natural 1 while using Full Auto, the weapon jams.

Reloading & Jams

• Reload (magazine swap): Requires an Action to replace a magazine (using the weapon’s reload property).
• Quick swap: If you have a free hand and a spare magazine ready, you may spend a Bonus Action to swap magazines (DM may restrict if surprised or grappled).
• Jam: When a jam occurs (natural 1 on the attack roll while Burst or Full Auto), the gun stops functioning immediately. To clear it:
  • Using Sleight of Hand or a tinker/Smith’s Tools check DC 12 as an Action success clears the jam.
  • Alternatively, spending an Action to force it open with Strength (Athletics) at DC 15 clears the jam but deals 1d4 bludgeoning to the weapon (DM may call for repairs later).
  • A long rest with proper tools fully clears and cleans the weapon.

Optional: Misfire & Maintenance (flavor/balance)

• If the weapon is used while dirty/poorly maintained (DM call), increase Jam DC by +2 and increase chance of a jam (e.g., jam on natural 1 2 instead of only natural 1).
• Repairing a damaged submachine gun requires a short rest and Smith’s Tools check (DC 13) or specialized gunsmithing over several hours.

Suggested DC Summary (quick reference)

• Sleight of Hand / Tinker to clear jam: DC 12 (Action)
• Force open (Athletics) to clear jam: DC 15 (Action; 1d4 weapon damage)
• Recoil save after >3 rounds fired (Con): DC 12 (fail = disadvantage next turn)
• Reload (swap mag): Action (Bonus Action if spare mag & free hand)

Balance & DM Notes

• This stat block aims to keep firearms exciting but not game-breaking. Semi-Auto roughly matches a heavy crossbow’s DPR but with longer range; Burst and Full‑Auto trade accuracy for damage/area pressure.
• If you use full‑auto frequently, enforce recoil and ammo scarcity (magazine cost, ammo weight) to prevent abuse.
• Feel free to tweak damage dice upward/downward (e.g., 1d10 instead of 1d8) if your table prefers higher lethality or grittier play.

Proficiency with a Heavy Crossbow allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Ammunition, Heavy, Loading, Range, Two-Handed, Push