Take some thing away form some one and they want it even more. The lesson of Gun bans and Prohibition.
And a horde of trigger-happy people with guns won't help in anyway, only fatten the coffers of gun merchants and producers...if only you've seen the news of how mainland Chinese settle disputes. Proliferation of firearms in China would drive up the "death by gunshot" statistics, though not enough to make "one-child policy" a history I afraid.
In China, various effective apparatus for civil society is still not fully in place, so if and when disputes can't be settled with RMB, violence is the most likely recourse. Under such environment, gun proliferation would inevitably presented lethal solution as the "faster, cheaper" option...and we all know how much the Chinese love the "faster, cheaper" option.
With active insurgencies in various border regions, easy access to firearms - even if restricted in some provinces - would make things worse via cross-province arms smuggling.