Tutorial — Fire from Blueprint

Goal: a pawn that fires automatic Mass projectiles from the camera while the fire button is held, and cycles projectile types with a key.

Time: 15 minutes. Result: the same logic as the shipped BP_DemoShooterPawn (open it to compare).

This tutorial uses the direct Spawn Projectiles call, which is ideal for single-player, AI turrets, and scripted volleys. For a player weapon in a multiplayer game, use the Mass Projectile Fire component instead (Tutorial 8). It adds client prediction and a validated server RPC.

#The two nodes that matter

Fire Projectiles (Mass Projectiles category) is the same call with a world context instead of a subsystem target. Use whichever reads better.

#Step 1 — Variables

Create a Pawn (or Character) Blueprint and add:

#Step 2 — FireRounds (function)

Create a function FireRounds with an Integer input Rounds:

1. Branch on Rounds > 0; return on False.
2. Get Actor Eyes View Point (self) → Out Location, Out Rotation.
3. Get Forward Vector (Out Rotation) → Direction.
4. Origin = Out Location + Direction × MuzzleOffsetCm.
5. Make Projectile Fire Event: Origin, Direction, Count = Rounds, Spread Half Angle Deg = SpreadHalfAngleDeg. Leave Speed at 0 and Random Seed at 0.
6. Get Projectile Subsystem → Spawn Projectiles with Type Config = ProjectileTypes[TypeIndex] (array Get) and the fire event.

Rounds goes into Count, so a frame that owes three rounds fires them in one call. Batching like this is what keeps 20,000-round volleys cheap.

#Step 3 — Automatic fire with an accumulator

Firing from a timer drifts at high RPM. Accumulate time on Event Tick instead:

1. Input: Fire Pressed → set bTriggerHeld = true, FireAccumulator = 1.0 (the first round fires immediately).
2. Input: Fire Released → set bTriggerHeld = false.
3. Event Tick → Branch bTriggerHeld:
   • FireAccumulator += DeltaSeconds × RoundsPerMinute / 60
   • Rounds = Floor(FireAccumulator), then FireAccumulator -= Rounds
   • FireRounds(Rounds)

The Mass Projectile Fire component implements this for you (Reset Fire Accumulator, Consume Fire Rounds); see Tutorial 8.

#Step 4 — Cycle types and clear

• Input: Next Type → TypeIndex = (TypeIndex + 1) % Length(ProjectileTypes).
• Input: Clear → Clear Projectiles (Mass Projectiles category). On a server this also clears every client.

#Step 5 — Test

Place the pawn (or set it as Default Pawn Class in your Game Mode) and press Play. Hold fire: tracers stream from the camera. If you see nothing, check Troubleshooting.

#Variations

Shotgun: set Count to the pellet count (for example 9) and Spread Half Angle Deg to 4. All pellets come from one fire event.

Muzzle socket: replace step 2 with the weapon mesh's Get Socket Location / Get Socket Rotation (Muzzle). Keep the camera direction if you want shots to converge on the crosshair.

Custom speed per shot: set Speed (cm/s) on the fire event, for example for a charge-up weapon. 0 uses the type's Default Speed.

Fountain / stress test: StressVolley in the demo pawn fires StressCount rounds in a single call. The console equivalent is proj.SpawnStress 20000.

#Networking note

On a server or standalone machine, Spawn Projectiles automatically replicates the shot to all clients (if the type is listed in Replicated Types). On a client, it spawns locally only and nobody else sees it. For player-controlled weapons in multiplayer, go to Tutorial 8 and Tutorial 10.