diff --git a/OpenRA.Game/GameRules/WeaponInfo.cs b/OpenRA.Game/GameRules/WeaponInfo.cs
index d60af0d190..973ee5b574 100644
--- a/OpenRA.Game/GameRules/WeaponInfo.cs
+++ b/OpenRA.Game/GameRules/WeaponInfo.cs
@@ -31,7 +31,8 @@ namespace OpenRA.GameRules
 		public Target GuidedTarget;
 	}
 
-	public interface IProjectileInfo { IEffect Create(ProjectileArgs args); }
+	public interface IProjectile : IEffect { }
+	public interface IProjectileInfo { IProjectile Create(ProjectileArgs args); }
 
 	public sealed class WeaponInfo
 	{
diff --git a/OpenRA.Game/Network/SyncReport.cs b/OpenRA.Game/Network/SyncReport.cs
index 3cb7bd2b16..4dc3ce1ec8 100644
--- a/OpenRA.Game/Network/SyncReport.cs
+++ b/OpenRA.Game/Network/SyncReport.cs
@@ -77,20 +77,16 @@ namespace OpenRA.Network
 							NamesValues = DumpSyncTrait(syncHash.Trait)
 						});
 
-			foreach (var e in orderManager.World.Effects)
+			foreach (var sync in orderManager.World.SyncedEffects)
 			{
-				var sync = e as ISync;
-				if (sync != null)
-				{
-					var hash = Sync.Hash(sync);
-					if (hash != 0)
-						report.Effects.Add(new EffectReport()
-						{
-							Name = sync.GetType().Name,
-							Hash = hash,
-							NamesValues = DumpSyncTrait(sync)
-						});
-				}
+				var hash = Sync.Hash(sync);
+				if (hash != 0)
+					report.Effects.Add(new EffectReport()
+					{
+						Name = sync.GetType().Name,
+						Hash = hash,
+						NamesValues = DumpSyncTrait(sync)
+					});
 			}
 		}
 
diff --git a/OpenRA.Game/World.cs b/OpenRA.Game/World.cs
index c358be5dab..cc8b3393ae 100644
--- a/OpenRA.Game/World.cs
+++ b/OpenRA.Game/World.cs
@@ -14,6 +14,7 @@ using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Effects;
 using OpenRA.FileFormats;
+using OpenRA.GameRules;
 using OpenRA.Graphics;
 using OpenRA.Network;
 using OpenRA.Orders;
@@ -30,6 +31,8 @@ namespace OpenRA
 		internal readonly TraitDictionary TraitDict = new TraitDictionary();
 		readonly SortedDictionary<uint, Actor> actors = new SortedDictionary<uint, Actor>();
 		readonly List<IEffect> effects = new List<IEffect>();
+		readonly List<ISync> syncedEffects = new List<ISync>();
+
 		readonly Queue<Action<World>> frameEndActions = new Queue<Action<World>>();
 
 		public int Timestep;
@@ -272,9 +275,27 @@ namespace OpenRA
 				t.RemovedFromWorld(a);
 		}
 
-		public void Add(IEffect b) { effects.Add(b); }
-		public void Remove(IEffect b) { effects.Remove(b); }
-		public void RemoveAll(Predicate<IEffect> predicate) { effects.RemoveAll(predicate); }
+		public void Add(IEffect e)
+		{
+			effects.Add(e);
+			var se = e as ISync;
+			if (se != null)
+				syncedEffects.Add(se);
+		}
+
+		public void Remove(IEffect e)
+		{
+			effects.Remove(e);
+			var se = e as ISync;
+			if (se != null)
+				syncedEffects.Remove(se);
+		}
+
+		public void RemoveAll(Predicate<IEffect> predicate)
+		{
+			effects.RemoveAll(predicate);
+			syncedEffects.RemoveAll(e => predicate((IEffect)e));
+		}
 
 		public void AddFrameEndTask(Action<World> a) { frameEndActions.Enqueue(a); }
 
@@ -334,6 +355,7 @@ namespace OpenRA
 
 		public IEnumerable<Actor> Actors { get { return actors.Values; } }
 		public IEnumerable<IEffect> Effects { get { return effects; } }
+		public IEnumerable<ISync> SyncedEffects { get { return syncedEffects; } }
 
 		public Actor GetActorById(uint actorId)
 		{
@@ -356,24 +378,20 @@ namespace OpenRA
 				var n = 0;
 				var ret = 0;
 
-				// hash all the actors
+				// Hash all the actors.
 				foreach (var a in Actors)
 					ret += n++ * (int)(1 + a.ActorID) * Sync.HashActor(a);
 
-				// hash all the traits that tick
+				// Hash all the traits that tick.
 				foreach (var actor in ActorsHavingTrait<ISync>())
 					foreach (var syncHash in actor.SyncHashes)
 						ret += n++ * (int)(1 + actor.ActorID) * syncHash.Hash;
 
-				// TODO: don't go over all effects
-				foreach (var e in Effects)
-				{
-					var sync = e as ISync;
-					if (sync != null)
-						ret += n++ * Sync.Hash(sync);
-				}
+				// Hash game state relevant effects such as projectiles.
+				foreach (var sync in SyncedEffects)
+					ret += n++ * Sync.Hash(sync);
 
-				// Hash the shared rng
+				// Hash the shared random number generator.
 				ret += SharedRandom.Last;
 
 				return ret;
diff --git a/OpenRA.Mods.Cnc/Effects/IonCannon.cs b/OpenRA.Mods.Cnc/Effects/IonCannon.cs
index c00aad2d79..e710ebf7f9 100644
--- a/OpenRA.Mods.Cnc/Effects/IonCannon.cs
+++ b/OpenRA.Mods.Cnc/Effects/IonCannon.cs
@@ -18,7 +18,7 @@ using OpenRA.Traits;
 
 namespace OpenRA.Mods.Cnc.Effects
 {
-	public class IonCannon : IEffect
+	public class IonCannon : IProjectile
 	{
 		readonly Target target;
 		readonly Animation anim;
diff --git a/OpenRA.Mods.Common/Effects/NukeLaunch.cs b/OpenRA.Mods.Common/Effects/NukeLaunch.cs
index eec0589d93..f8f0ce1be3 100644
--- a/OpenRA.Mods.Common/Effects/NukeLaunch.cs
+++ b/OpenRA.Mods.Common/Effects/NukeLaunch.cs
@@ -19,7 +19,7 @@ using OpenRA.Traits;
 
 namespace OpenRA.Mods.Common.Effects
 {
-	public class NukeLaunch : IEffect
+	public class NukeLaunch : IProjectile
 	{
 		readonly Player firedBy;
 		readonly Animation anim;
diff --git a/OpenRA.Mods.Common/Projectiles/AreaBeam.cs b/OpenRA.Mods.Common/Projectiles/AreaBeam.cs
index 5e38dd48f8..1f72ab7c96 100644
--- a/OpenRA.Mods.Common/Projectiles/AreaBeam.cs
+++ b/OpenRA.Mods.Common/Projectiles/AreaBeam.cs
@@ -69,14 +69,14 @@ namespace OpenRA.Mods.Common.Projectiles
 		[Desc("Beam color is the player's color.")]
 		public readonly bool UsePlayerColor = false;
 
-		public IEffect Create(ProjectileArgs args)
+		public IProjectile Create(ProjectileArgs args)
 		{
 			var c = UsePlayerColor ? args.SourceActor.Owner.Color.RGB : Color;
 			return new AreaBeam(this, args, c);
 		}
 	}
 
-	public class AreaBeam : IEffect, ISync
+	public class AreaBeam : IProjectile, ISync
 	{
 		readonly AreaBeamInfo info;
 		readonly ProjectileArgs args;
diff --git a/OpenRA.Mods.Common/Projectiles/Bullet.cs b/OpenRA.Mods.Common/Projectiles/Bullet.cs
index ba1aebdc4a..3d4685a9b9 100644
--- a/OpenRA.Mods.Common/Projectiles/Bullet.cs
+++ b/OpenRA.Mods.Common/Projectiles/Bullet.cs
@@ -82,10 +82,10 @@ namespace OpenRA.Mods.Common.Projectiles
 		public readonly int ContrailDelay = 1;
 		public readonly WDist ContrailWidth = new WDist(64);
 
-		public IEffect Create(ProjectileArgs args) { return new Bullet(this, args); }
+		public IProjectile Create(ProjectileArgs args) { return new Bullet(this, args); }
 	}
 
-	public class Bullet : IEffect, ISync
+	public class Bullet : IProjectile, ISync
 	{
 		readonly BulletInfo info;
 		readonly ProjectileArgs args;
diff --git a/OpenRA.Mods.Common/Projectiles/GravityBomb.cs b/OpenRA.Mods.Common/Projectiles/GravityBomb.cs
index 1d1589d6fa..90204d18da 100644
--- a/OpenRA.Mods.Common/Projectiles/GravityBomb.cs
+++ b/OpenRA.Mods.Common/Projectiles/GravityBomb.cs
@@ -39,10 +39,10 @@ namespace OpenRA.Mods.Common.Projectiles
 		[Desc("Value added to speed every tick.")]
 		public readonly WDist Acceleration = new WDist(15);
 
-		public IEffect Create(ProjectileArgs args) { return new GravityBomb(this, args); }
+		public IProjectile Create(ProjectileArgs args) { return new GravityBomb(this, args); }
 	}
 
-	public class GravityBomb : IEffect, ISync
+	public class GravityBomb : IProjectile, ISync
 	{
 		readonly GravityBombInfo info;
 		readonly Animation anim;
diff --git a/OpenRA.Mods.Common/Projectiles/LaserZap.cs b/OpenRA.Mods.Common/Projectiles/LaserZap.cs
index c5928ffa17..2819396213 100644
--- a/OpenRA.Mods.Common/Projectiles/LaserZap.cs
+++ b/OpenRA.Mods.Common/Projectiles/LaserZap.cs
@@ -47,14 +47,14 @@ namespace OpenRA.Mods.Common.Projectiles
 
 		[PaletteReference] public readonly string HitAnimPalette = "effect";
 
-		public IEffect Create(ProjectileArgs args)
+		public IProjectile Create(ProjectileArgs args)
 		{
 			var c = UsePlayerColor ? args.SourceActor.Owner.Color.RGB : Color;
 			return new LaserZap(args, this, c);
 		}
 	}
 
-	public class LaserZap : IEffect
+	public class LaserZap : IProjectile
 	{
 		readonly ProjectileArgs args;
 		readonly LaserZapInfo info;
diff --git a/OpenRA.Mods.Common/Projectiles/Missile.cs b/OpenRA.Mods.Common/Projectiles/Missile.cs
index cfdd9b2c20..b3fd256085 100644
--- a/OpenRA.Mods.Common/Projectiles/Missile.cs
+++ b/OpenRA.Mods.Common/Projectiles/Missile.cs
@@ -141,11 +141,11 @@ namespace OpenRA.Mods.Common.Projectiles
 			"not trigger fast enough, causing the missile to fly past the target.")]
 		public readonly WDist CloseEnough = new WDist(298);
 
-		public IEffect Create(ProjectileArgs args) { return new Missile(this, args); }
+		public IProjectile Create(ProjectileArgs args) { return new Missile(this, args); }
 	}
 
 	// TODO: double check square roots!!!
-	public class Missile : IEffect, ISync
+	public class Missile : IProjectile, ISync
 	{
 		enum States
 		{
diff --git a/OpenRA.Mods.RA/Projectiles/TeslaZap.cs b/OpenRA.Mods.RA/Projectiles/TeslaZap.cs
index 63995f222d..8b7302e809 100644
--- a/OpenRA.Mods.RA/Projectiles/TeslaZap.cs
+++ b/OpenRA.Mods.RA/Projectiles/TeslaZap.cs
@@ -32,10 +32,10 @@ namespace OpenRA.Mods.RA.Projectiles
 
 		public readonly int Duration = 2;
 
-		public IEffect Create(ProjectileArgs args) { return new TeslaZap(this, args); }
+		public IProjectile Create(ProjectileArgs args) { return new TeslaZap(this, args); }
 	}
 
-	public class TeslaZap : IEffect
+	public class TeslaZap : IProjectile
 	{
 		readonly ProjectileArgs args;
 		readonly TeslaZapInfo info;