There are several semi autos with oversize charging handles.From what I remember, there was an issue with the way that gun locked up and it unlocked on me blowing bits of the case, haven't heard of it happening to anyone else, just don't trust them personally anymore. I have a lot of trouble racking the bolt on a semi, unfortunately. I don't mind keeping it loaded but would not be comfortable having to clear a jam or something.
Look into a stock sleeve to hold a few rounds on your single shot.
A good dog is always my first line of defense. Like you, I have had them run off unwanted people without needing to do anything besides get him a treat.