A different way of defining what an assault weapon is

[Always Right]

20. Over inclusive and under inclusive at the same time

Any semi-automatic centerfire rifle or brace-equipped-pistol capable of accepting detachable magazines or belted ammunition.

The problem with that definition is that nearly every semi-auto rifle, including the type most commonly used for hunting, meet that definition. The flaw there is the word "capable" as it is very vague. Semi-auto guns need to feed from somewhere and unless the ammunition holding area is machined as part of the receiver from a large block of metal (which is not very efficient and real expensive), then they have a magazine. These magazines are manufactured separately and then assembled later. These magazines can be detached for cleaning and repair (such as replacing the spring, which is what generally what wears out. If the magazines don't detach, then it is an engineering challenge to be able to remove the spring and follower from the top as the top needs to be small enough to hold the ammo in (as well as hold the follower and spring in when the ammo is gone).

The only semi-automatic center fire rifle that comes to mind which wouldn't be banned under your definition of assault weapon that I can think up would be the Military's M1 Garand rifle. That particular rifle is available to anyone as it is not a full auto, it was the military's main battle rifle for over 20 years and has probably killed more people than any one gun model ever, in part due to it's powerful 30.06 ammo (substantially more powerful than an AR-15's ammo) and that it has been used by the US in multiple wars.

Since you named magazine and belted, what happens when a new feeding method is developed and the guns are unbanned?