A method of coating an inner surface of a weapon barrel includes the following steps: introducing a plasma burner into the weapon barrel; producing a plasma flame by the plasma burner; directing the plasma flame against the inner barrel surface to cause impingement thereon; introducing a coating material in powder, wire or ribbon form into the plasma flame for melting the coating material to form a molten liquid and for depositing the molten liquid by the plasma flame on the inner barrel surface; and moving the plasma burner inside the weapon barrel axially thereof and relative thereto while performing the depositing step for obtaining a surface coating on the inner barrel surface.