[citation needed]
Would-be tyrants get power (and stay in power) by gaining the support of people capable of projecting force and power onto the populace. From the perspective of tyranny, it is irrelevant if their supporters are i.e. the military or a bunch of militia guys who have acquired their guns privately.
Source: Many, many civil wars across history.
Trying to guard against tyranny by increasing private gun ownership is dumb, because you are simply creating another group of people that would-be tyrants can use to gain and retain power.
Actualy tyranny-proofing a society involves building a strong network of institutions (as in laws, civil society, courts, legislative bodies, distributed wealth and sets of norms) that can effectively counteract the attempt of any one group or individual to centralize power.
Also: even if you completely disarm a society and armed resistance becomes necessary in the future (for example western and northern European countries under Nazi occupation during WWII), getting access to firearms is usually not the hardest, nor the most important part of building an effective resistance movement. The organizational part and effective operational security is much harder and more important.