[AS3] Help with Bullet Array

I am creating a simple game and whenever i shoot bullets, the game becomes VERY laggy. I have a movieclip for bullets and i use an array to control it. Here is the code that i have in my MAIN file:

package 
{
	import flash.display.MovieClip;
	import flash.events.Event;
	import flash.events.MouseEvent;

	public class main extends MovieClip
	{
		private var _enemy:Number;
		private var _bullets:Array;
		private var _damage:Number;
		
		public function main()
		{
			_enemy = 10;
			_damage = 5;
			_bullets = new Array();
			_bullets = [];
			stage.addEventListener("bulletCreated", onBulletCreated);
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
		}
		private function onBulletCreated(event:Event)
		{
			_bullets.push(MovieClip(event.target));
			trace(event.target.name);
		}
		public function onEnterFrame(event:Event):void
		{
		for (var j:int = 0; j < _bullets.length; j++)
				{
					//Top
					if (_bullets[j].hitTestObject(enemy))
					{
						removeChild(_bullets[j]);
						_bullets.splice(j,1);
						j--;
					}
					
				}
		}
		 
		 public function checkCollisionWithPlayer(wall:MovieClip)
		{
				Collision.block(player, wall);
		}
		
	}
}

Any suggestions as to why the game is so laggy?