It's very easy to repel the Lao-Shan Lung with a light bowgun, just drink a demondrug or mega demondrug to make yourself a bit stronger and take a bow with pierce S lv1, lv2, lv3's and fire or dragon bullets. If you use pierce S just make sure you shoot strait through its head so the bullet does maximum damage. A bowgun with rapid fire pierce S and an armor S will make the pierce bullets stronger, just start with pierce S and when you run out of them just use your fire or dragon bullets and after thos use normal lv3's.