When shotguns and rifles are used in crime, theres a good chance they are sawed-off or fully automatic which makes them illegal already. You cannot just buy these weapons at stores.

Even in Canada, where 8.5 inch barrels and pistol grips are legal for pump actions and can be bought as easily as candy, criminals are too cheap and will just illegally saw off guns anyways. They don't really care about the extra offense of illegally modifying a gun.

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"Conservatives are not necessarily stupid, but most stupid people are conservatives." — John Stuart Mill