Add script inheriting from scriptableobject to game object

I have a script called Weapon.cs, which is a scriptable object.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public abstract class Weapon : ScriptableObject {

protected Camera _mainCamera;
protected Transform _weaponTransform;
protected int _damage;
protected int _fireRatePerSecond;
protected bool _isAutomaticWeapon;

protected void FireWeapon()
{
    //if the weapon is automatic
    if (_isAutomaticWeapon)
    {
        ShootRapidFireOnMouseHold();
    }
    //if the weapon is semi automatic
    else
    {
        ShootSingleBulletOnMouseClick();
    }
}

protected void MoveWeaponWithCamera(Transform weaponTransform)
{
    _weaponTransform.rotation = _mainCamera.transform.rotation; //temporary way of making sure the gun moves with the camera
}

protected void ShootSingleBulletOnMouseClick()
{
    if (Input.GetKeyDown(KeyCode.Mouse0)) //if left mouse button is clicked
    {
        CastRay();
    }
}

protected void ShootRapidFireOnMouseHold()
{
    if (Input.GetKey(KeyCode.Mouse0)) //if left mouse button is held down
    {
        CastRay(); //rapid fire
        //PlayShootAnimation();
    }
}

protected void CastRay()
{
    RaycastHit hit;
    if (Physics.Raycast(_mainCamera.transform.position, _mainCamera.transform.forward, out hit, 100))
    {
        Debug.Log(hit.transform.name);
    }
}
//protected abstract void PlayShootAnimation();
}

I have a second script called MachineGun.cs, which inherits from Weapon.cs, and thus indirectly from scriptable object.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class MachineGun : Weapon{

private GameObject _machineGunBarrel;

//private float _animationVelocity;

// Use this for initialization
void Start () {
    //initialize the basic properties of a weapon
    _damage = 7;
    _fireRatePerSecond = 10;
    _isAutomaticWeapon = true;

    _weaponTransform = GameObject.Find("Weapon_MachineGun").transform;
    _machineGunBarrel = GameObject.Find("machinegun_p1");

    _mainCamera = Camera.main;

}

// Update is called once per frame
void Update () {
    MoveWeaponWithCamera(_weaponTransform);
    FireWeapon();
}

//protected override void Shoot()
//{
//    RaycastHit hit;
//    if(Physics.Raycast(_mainCamera.transform.position, _mainCamera.transform.forward, out hit, 100))
//    {
//        Debug.Log(hit.transform.name);
//    }
//}

void PlayShootAnimation()
{
    _machineGunBarrel.transform.RotateAround(_machineGunBarrel.transform.up, _fireRatePerSecond * Time.deltaTime);
    PlayShootAnimation(); //play the shoot animation of the gun
}
}

It's currently impossible, since MachineGun.cs doesn't inherit from monobehaviour anymore.

I have a weapon gameobject in my scene, and so here's my question: How do I go about adding the MachineGun.cs script as a component to my weapon gameobject? Or since this is impossible,

How should I build a weapon system with a general Weapon.cs script from which all weapons can inherit basic functions and fields/variables?

EDIT 1: provided code to my post and added the "why I wanna do this".

Thanks in advance!