diff --git a/server/gameserver/bullet.cc b/server/gameserver/bullet.cc
index b275c55..c2084f7 100644
--- a/server/gameserver/bullet.cc
+++ b/server/gameserver/bullet.cc
@@ -33,6 +33,7 @@ void Bullet::Initialize()
     RecalcSelfCollider();
     ability_ = sender.Get()->GetAbility();
     is_curr_weapon = sender.Get()->GetCurrWeapon()->meta == gun_meta;
+    create_frameno_ = room->GetFrameNo();
 }
 
 void Bullet::Update(int delta_time)
@@ -588,3 +589,8 @@ void Bullet::AddGunBuff()
         sender.Get()->context_ability = old_context_ability;
     }
 }
+
+bool Bullet::IsPreBattleBullet()
+{
+    return create_frameno_ <= room->GetBattleStartFrameNo();
+}
diff --git a/server/gameserver/bullet.h b/server/gameserver/bullet.h
index dd4f2bd..f4a4fc5 100644
--- a/server/gameserver/bullet.h
+++ b/server/gameserver/bullet.h
@@ -41,6 +41,7 @@ class Bullet : public MoveableEntity
     float GetAtk();
     float GetExplosionRange();
     bool IsCurrWeapon();
+    bool IsPreBattleBullet();
 
 protected:
     Bullet();
@@ -67,6 +68,7 @@ private:
     std::shared_ptr<Ability> ability_;
     bool is_curr_weapon = false;
     std::set<int> hit_objects_;
+    long long create_frameno_ = 0;
 
     friend class EntityFactory;
 };
diff --git a/server/gameserver/car.cc b/server/gameserver/car.cc
index b127dec..773d071 100644
--- a/server/gameserver/car.cc
+++ b/server/gameserver/car.cc
@@ -291,10 +291,12 @@ void Car::OnBulletHit(Bullet* bullet)
         if (bullet->meta->buff_meta) {
             MustBeAddBuff(bullet->sender.Get(), bullet->meta->i->buffid());
         }
-        DecHP(finaly_dmg,
-              bullet->sender.Get()->GetUniId(),
-              bullet->sender.Get()->GetName(),
-              bullet->gun_meta->i->id());
+        if (!bullet->IsPreBattleBullet()) {
+            DecHP(finaly_dmg,
+                  bullet->sender.Get()->GetUniId(),
+                  bullet->sender.Get()->GetName(),
+                  bullet->gun_meta->i->id());
+        }
         if (bullet->meta->buff_meta) {
             MustBeAddBuff(this, bullet->meta->i->buffid());
         }
diff --git a/server/gameserver/creature.cc b/server/gameserver/creature.cc
index 89bd1b7..a1e780a 100644
--- a/server/gameserver/creature.cc
+++ b/server/gameserver/creature.cc
@@ -42,9 +42,8 @@ static void InternalCreateBullet(BulletInfo& bullet_info)
     }
     if (bullet_info.delay_time <= 0) {
         int bullet_uniid = 0;
-        if (c->room->BattleStarted() ||
-            (c->room->GetGasData().gas_mode == GasJump &&
-             !c->HasBuffEffect(kBET_Jump))) {
+        if (MetaMgr::Instance()->prebattle_can_use_skill ||
+            !(c->HasBuffEffect(kBET_Jump) || c->HasBuffEffect(kBET_Fly))) {
             bullet_uniid = c->room->CreateBullet
                 (c,
                  c->shot_passenger,
@@ -56,9 +55,7 @@ static void InternalCreateBullet(BulletInfo& bullet_info)
                  bullet_info.fly_distance,
                  bullet_info.is_tank_skin);
         }
-        if (bullet_uniid == 0) {
-            bullet_uniid = c->room->AllocUniid();
-        }
+        bullet_uniid = bullet_uniid ? bullet_uniid : c->room->AllocUniid();
         c->room->frame_event.AddBullet
             (bullet_uniid,
              c->GetWeakPtrRef(),
@@ -70,7 +67,7 @@ static void InternalCreateBullet(BulletInfo& bullet_info)
     } else {
         BulletInfo* info_copy = new BulletInfo();
         *info_copy = bullet_info;
-        bullet_info.c.Get()->room->xtimer.AddDeadLineTimerAndAttach
+        xtimer_list* timer = bullet_info.c.Get()->room->xtimer.AddDeadLineTimerAndAttach
             (
              bullet_info.delay_time / FRAME_RATE_MS,
              a8::XParams()
@@ -88,6 +85,9 @@ static void InternalCreateBullet(BulletInfo& bullet_info)
                  delete info_copy;
              }
              );
+        if (!c->room->BattleStarted()) {
+            c->room->AddToPostBattleAutoFreeList(timer);
+        }
     }
 }
 
diff --git a/server/gameserver/hero.cc b/server/gameserver/hero.cc
index 5627097..9632348 100644
--- a/server/gameserver/hero.cc
+++ b/server/gameserver/hero.cc
@@ -131,10 +131,12 @@ void Hero::OnBulletHit(Bullet* bullet)
         if (bullet->meta->buff_meta) {
             MustBeAddBuff(bullet->sender.Get(), bullet->meta->i->buffid());
         }
-        DecHP(finaly_dmg,
-              bullet->sender.Get()->GetUniId(),
-              bullet->sender.Get()->GetName(),
-              bullet->gun_meta->i->id());
+        if (!bullet->IsPreBattleBullet()) {
+            DecHP(finaly_dmg,
+                  bullet->sender.Get()->GetUniId(),
+                  bullet->sender.Get()->GetName(),
+                  bullet->gun_meta->i->id());
+        }
     }
 }
 
diff --git a/server/gameserver/human.cc b/server/gameserver/human.cc
index d1a11ed..f9842f4 100644
--- a/server/gameserver/human.cc
+++ b/server/gameserver/human.cc
@@ -3618,15 +3618,19 @@ void Human::OnBulletHit(Bullet* bullet)
             MustBeAddBuff(bullet->sender.Get(), bullet->meta->i->buffid());
         }
         if (bullet->sender.Get() && bullet->sender.Get()->IsCar() && bullet->passenger.Get()) {
-            DecHP(finaly_dmg,
-                  bullet->passenger.Get()->GetUniId(),
-                  bullet->passenger.Get()->GetName(),
-                  bullet->gun_meta->i->id());
+            if (!bullet->IsPreBattleBullet()) {
+                DecHP(finaly_dmg,
+                      bullet->passenger.Get()->GetUniId(),
+                      bullet->passenger.Get()->GetName(),
+                      bullet->gun_meta->i->id());
+            }
         } else {
-            DecHP(finaly_dmg,
-                  bullet->sender.Get()->GetUniId(),
-                  bullet->sender.Get()->GetName(),
-                  bullet->gun_meta->i->id());
+            if (!bullet->IsPreBattleBullet()) {
+                DecHP(finaly_dmg,
+                      bullet->sender.Get()->GetUniId(),
+                      bullet->sender.Get()->GetName(),
+                      bullet->gun_meta->i->id());
+            }
         }
 #ifdef DEBUG
         bullet->sender.Get()->SendDebugMsg
diff --git a/server/gameserver/obstacle.cc b/server/gameserver/obstacle.cc
index b27e8af..99a8655 100644
--- a/server/gameserver/obstacle.cc
+++ b/server/gameserver/obstacle.cc
@@ -472,6 +472,9 @@ void Obstacle::OnBulletHit(Bullet* bullet)
     if (meta->i->bullet_hit() == kBulletHitEatDmg) {
         return;
     }
+    if (bullet->IsPreBattleBullet()) {
+        return;
+    }
     if (!IsDead(bullet->room) &&
         !IsTerminatorAirDropBox(bullet->room)) {
         if (meta->receive_special_damage_type != 0 &&
diff --git a/server/gameserver/room.cc b/server/gameserver/room.cc
index aeff713..4a1015d 100644
--- a/server/gameserver/room.cc
+++ b/server/gameserver/room.cc
@@ -1399,6 +1399,7 @@ void Room::UpdateGasJump()
             InitAirDrop();
             InitAirRaid();
         }
+        ClearPostBattleAutoFreeList();
     }
 }
 
@@ -4000,3 +4001,33 @@ void Room::AirRaid(int airraid_id)
          raid_cb,
          &xtimer_attacher_.timer_list_);
 }
+
+void Room::AddToPostBattleAutoFreeList(xtimer_list* timer)
+{
+    if (BattleStarted()) {
+        abort();
+    }
+    if (!timer) {
+        abort();
+    }
+    if (post_battle_auto_free_list_.find(timer) != post_battle_auto_free_list_.end()) {
+        abort();
+    }
+    auto cb =
+        [this] (xtimer_list* timer)
+        {
+            post_battle_auto_free_list_.erase(timer);
+        };
+    xtimer.AddTimerDestoryHandle(timer, cb);
+    post_battle_auto_free_list_.insert(timer);
+}
+
+void Room::ClearPostBattleAutoFreeList()
+{
+    while (!post_battle_auto_free_list_.empty()) {
+        for (xtimer_list* timer : post_battle_auto_free_list_) {
+            xtimer.DeleteTimer(timer);
+            break;
+        }
+    }
+}
diff --git a/server/gameserver/room.h b/server/gameserver/room.h
index 2b2cf0c..307acd3 100644
--- a/server/gameserver/room.h
+++ b/server/gameserver/room.h
@@ -188,6 +188,7 @@ public:
     void GetPartObjectWatchList(Entity* entity, std::vector<Human*>& watch_list);
     void SetInfiniteBulletMode();
     bool IsInfiniteBulletMode() { return infinite_bullet_mode_; };
+    void AddToPostBattleAutoFreeList(xtimer_list* timer);
 
 private:
     void ShuaAndroid();
@@ -269,6 +270,7 @@ private:
     void InitAndroidAI();
     void ForwardGasRing(int n);
     void InternalRemoveObjectLater(Entity* entity, a8::XTimerAttacher& entity_xtimer_attacher);
+    void ClearPostBattleAutoFreeList();
 
     #ifdef DEBUG
     void InitDebugInfo();
@@ -340,6 +342,8 @@ private:
 
     std::vector<ObstacleData> obstacle_datas_;
 
+    std::set<xtimer_list*> post_battle_auto_free_list_;
+
     xtimer_list* auto_jump_timer_ = nullptr;
 
     Incubator* incubator_ = nullptr;
diff --git a/third_party/a8engine b/third_party/a8engine
index 8932713..5e0a939 160000
--- a/third_party/a8engine
+++ b/third_party/a8engine
@@ -1 +1 @@
-Subproject commit 8932713766a5c0289966f08a5a0153a1ae493a9d
+Subproject commit 5e0a939a89ba97edd371695432ef029eae2c55d5