I hunt similar conditions with a 20 gage smoothbore with fiber optic rifle style sights and rifled slugs. Your 12 gage shotgun is a much better choice for that application, and considerably more pleasant to shoot than that howitzer you're using. Scopes are nearly worthless at short range, and if sight aquisition becomes a problem because of low light conditions refit the gun with fiber optic sights. Slugs are absolutely better than high velocity rounds at ranges under 100 yards, and much safer.