Isn't worked

Content.Client/Weapons/Ranged/Systems/GunSystem.cs

@@ -4,6 +4,7 @@
 using Content.Client.Weapons.Ranged.Components;
 using Content.Shared.Camera;
 using Content.Shared.CombatMode;
+using Content.Shared.Mech.Components; // Corvax-Frontier
 using Content.Shared.Weapons.Ranged;
 using Content.Shared.Weapons.Ranged.Components;
 using Content.Shared.Weapons.Ranged.Events;
@@ -144,6 +145,13 @@ public override void Update(float frameTime)
 
         var entity = entityNull.Value;
 
+        // Corvax-Frontier addition start.
+        if (TryComp<MechPilotComponent>(entity, out var mechPilot))
+        {
+            entity = mechPilot.Mech;
+        }
+        // Corvax-Frontier addition end.
+
         if (!TryGetGun(entity, out var gunUid, out var gun))
         {
             return;

Content.Server/Atmos/EntitySystems/FlammableSystem.cs

@@ -12,6 +12,7 @@
 using Content.Shared.Damage;
 using Content.Shared.Database;
 using Content.Shared.Interaction;
+using Content.Shared.Mech.Components; // Corvax-Frontier
 using Content.Shared.Physics;
 using Content.Shared.Popups;
 using Content.Shared.Projectiles;
@@ -314,6 +315,11 @@ public void Ignite(EntityUid uid, EntityUid ignitionSource, FlammableComponent?
             if (!Resolve(uid, ref flammable))
                 return;
 
+            // Corvax-Frontier addition start.
+            if (TryComp<MechPilotComponent>(uid, out var mechPilot) && TryComp<MechComponent>(mechPilot.Mech, out var mech) && mech.Airtight)
+                return;
+            // Corvax-Frontier addition end.
+
             if (flammable.AlwaysCombustible)
             {
                 flammable.FireStacks = Math.Max(flammable.FirestacksOnIgnite, flammable.FireStacks);

Content.Server/Mech/Equipment/EntitySystems/CorvaxMechGunSystem.cs

@@ -0,0 +1,73 @@
+/*
+This code under CC-BY-SA 3.0, and taken from https://github.com/space-wizards/space-station-14/pull/19263/files#diff-b878680d623afff2ab173822240fcb66e3c989d11e9786490e6b91947383c198.
+*/
+
+using Content.Server.Mech.Systems;
+using Content.Server.Power.Components;
+using Content.Server.Power.EntitySystems;
+using Content.Shared.Mech.Components;
+using Content.Shared.Mech.Equipment.Components;
+using Content.Shared.Throwing;
+using Content.Shared.Weapons.Ranged.Systems;
+using Robust.Shared.Random;
+
+namespace Content.Server.Mech.Equipment.EntitySystems;
+public sealed class CorvaxMechGunSystem : EntitySystem
+{
+    [Dependency] private readonly IRobustRandom _random = default!;
+    [Dependency] private readonly ThrowingSystem _throwing = default!;
+    [Dependency] private readonly MechSystem _mech = default!;
+    [Dependency] private readonly BatterySystem _battery = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeLocalEvent<MechEquipmentComponent, GunShotEvent>(MechGunShot);
+    }
+
+    private void MechGunShot(EntityUid uid, MechEquipmentComponent component, ref GunShotEvent args)
+    {
+        if (!component.EquipmentOwner.HasValue)
+            return;
+
+        if (!TryComp<MechComponent>(component.EquipmentOwner.Value, out var mech))
+            return;
+
+        if (TryComp<BatteryComponent>(uid, out var battery))
+        {
+            ChargeGunBattery(uid, battery);
+            return;
+        }
+
+        foreach (var (ent, _) in args.Ammo)
+        {
+            if (ent.HasValue && mech.EquipmentContainer.Contains(ent.Value))
+            {
+                mech.EquipmentContainer.Remove(ent.Value);
+                _throwing.TryThrow(ent.Value, _random.NextVector2(), _random.Next(5));
+            }
+        }
+    }
+
+    private void ChargeGunBattery(EntityUid uid, BatteryComponent component)
+    {
+        if (!TryComp<MechEquipmentComponent>(uid, out var mechEquipment) || !mechEquipment.EquipmentOwner.HasValue)
+            return;
+
+        if (!TryComp<MechComponent>(mechEquipment.EquipmentOwner.Value, out var mech))
+            return;
+
+        var maxCharge = component.MaxCharge;
+        var currentCharge = component.CurrentCharge;
+
+        var chargeDelta = maxCharge - currentCharge;
+
+        if (chargeDelta <= 0 || mech.Energy - chargeDelta < 0)
+            return;
+
+        if (!_mech.TryChangeEnergy(mechEquipment.EquipmentOwner.Value, -chargeDelta, mech))
+            return;
+
+        _battery.SetCharge(uid, component.MaxCharge, component);
+    }
+}

Content.Server/Mech/Systems/MechSystem.cs

@@ -1,4 +1,5 @@
 using System.Linq;
+using Content.Server.Atmos.Components; // Corvax-Frontier
 using Content.Server.Atmos.EntitySystems;
 using Content.Server.Mech.Components;
 using Content.Server.Power.Components;

Content.Server/Weapons/Ranged/Systems/GunSystem.cs

@@ -2,6 +2,7 @@
 using System.Numerics;
 using Content.Server.Cargo.Systems;
 using Content.Server.Interaction;
+using Content.Server.Mech.Equipment.Components; // Corvax-Frontier
 using Content.Server.Power.EntitySystems;
 using Content.Server.Projectiles;
 using Content.Server.Stunnable;
@@ -11,6 +12,7 @@
 using Content.Shared.Database;
 using Content.Shared.Effects;
 using Content.Shared.Interaction.Components;
+using Content.Shared.Mech.Equipment.Components; // Corvax-Frontier
 using Content.Shared.Projectiles;
 using Content.Shared.Weapons.Melee;
 using Content.Shared.Weapons.Ranged;
@@ -130,6 +132,7 @@ protected override bool ShootDirect(EntityUid gunUid, GunComponent gun, EntityUi
 
                     result = true;
                     Dirty(ent!.Value, cartridge);
+
                     break;
                 // Ammo shoots itself
                 case AmmoComponent newAmmo:

Content.Shared/Mech/EntitySystems/SharedMechSystem.cs

@@ -15,6 +15,7 @@
 using Content.Shared.Movement.Systems;
 using Content.Shared.Popups;
 using Content.Shared.Weapons.Melee;
+using Content.Shared.Weapons.Ranged.Events;
 using Robust.Shared.Containers;
 using Robust.Shared.Network;
 using Robust.Shared.Serialization;

Content.Shared/Weapons/Ranged/Systems/SharedGunSystem.cs

@@ -11,6 +11,7 @@
 using Content.Shared.Gravity;
 using Content.Shared.Hands;
 using Content.Shared.Hands.Components;
+using Content.Shared.Mech.Components; // Corvax-Frontier
 using Content.Shared.Item; // Delta-V: Felinids in duffelbags can't shoot.
 using Content.Shared.Popups;
 using Content.Shared.Projectiles;
@@ -127,13 +128,16 @@
     {
         var user = args.SenderSession.AttachedEntity;
 
-        if (user == null ||
-            !_combatMode.IsInCombatMode(user) ||
-            !TryGetGun(user.Value, out var ent, out var gun) ||
-            HasComp<ItemComponent>(user)) // Delta-V: Felinids in duffelbags can't shoot.
-        {
+        if (user == null || !_combatMode.IsInCombatMode(user) || HasComp<ItemComponent>(user)) // Delta-V: Felinids in duffelbags can't shoot.
             return;
-        }
+
+        // Corvax-Frontier addition start.
+        if (TryComp<MechPilotComponent>(user.Value, out var mechPilot))
+            user = mechPilot.Mech;
+
+        if (!TryGetGun(user.Value, out var ent, out var gun))
+            return;
+        // Corvax-Frontier addition end.
 
         if (ent != GetEntity(msg.Gun))
             return;
@@ -146,15 +150,21 @@
     {
         var gunUid = GetEntity(ev.Gun);
 
-        if (args.SenderSession.AttachedEntity == null ||
-            !TryComp<GunComponent>(gunUid, out var gun) ||
-            !TryGetGun(args.SenderSession.AttachedEntity.Value, out _, out var userGun))
-        {
+        // Corvax-Frontier addition start.
+        var user = args.SenderSession.AttachedEntity;
+
+        if (user == null)
             return;
-        }
 
-        if (userGun != gun)
+        if (TryComp<MechPilotComponent>(user.Value, out var mechPilot))
+            user = mechPilot.Mech;
+
+        if (!TryGetGun(user.Value, out var ent, out var gun))
+            return;
+
+        if (ent != ev.Gun)
             return;
+        // Corvax-Frontier addition end.
 
         StopShooting(gunUid, gun);
     }
@@ -172,6 +182,17 @@
         gunEntity = default;
         gunComp = null;
 
+        // Corvax-Frontier addition start.
+        if (TryComp<MechComponent>(entity, out var mech) &&
+            mech.CurrentSelectedEquipment.HasValue &&
+            TryComp<GunComponent>(mech.CurrentSelectedEquipment.Value, out var mechGun))
+        {
+            gunEntity = mech.CurrentSelectedEquipment.Value;
+            gunComp = mechGun;
+            return true;
+        }
+        // Corvax-Frontier addition end.
+
         if (EntityManager.TryGetComponent(entity, out HandsComponent? hands) &&
             hands.ActiveHandEntity is { } held &&
             TryComp(held, out GunComponent? gun))
@@ -331,8 +352,11 @@
         var shots = 0;
         var lastFire = gun.NextFire;
 
+        Log.Debug($"Nextfire={gun.NextFire} curTime={curTime}"); // Corvax-Frontier addition.
+
         while (gun.NextFire <= curTime)
         {
+            Log.Debug("Shots++"); // Corvax-Frontier addition.
             gun.NextFire += fireRate;
             shots++;
         }
@@ -356,6 +380,8 @@
                 throw new ArgumentOutOfRangeException($"No implemented shooting behavior for {gun.SelectedMode}!");
         }
 
+        Log.Debug($"Shots fired: {shots}"); // Corvax-Frontier addition.
+
         var attemptEv = new AttemptShootEvent(user, null);
         RaiseLocalEvent(gunUid, ref attemptEv);