* Low capacity weapons should be more available than high capacity weapons.
* Slower firing weapons should more available than faster firing weapons.
* Difficult to hide weapons should be more available than easier to hide weapons.
* Safer weapons should be more available than less safe weapons.
By available, I mean a combination of economics, taxation, licensing, and regulation. The combination of these should be such that as a person seeks to go up the rungs, they will encounter a rising combination of economic, tax, licensing, and regulatory deterrents. If you are willing to face these burdens, then you can have whatever you want. Taxes should be enough so that the gun is affordable, meaning that it doesn't abridge your rights, but add up to enough so that you'll divest yourself of unnecessary guns. Licensing for basic weaponry should be pretty simple, while licensing for more dangerous models should require yearly time commitments and assessment.
In this scheme, bolt action hunting rifles and muskets should come in pretty "cheap," while military clones should add up to something expensive.
Of course, the devil is in the details. Implemented wrong, this approach is either ineffective or oppressive. If it's ineffective, it's not worth the political fight. If oppressive, it won't be passed or will be mercilessly opposed and poorly enforced, if enforced at all.