Demand for A2 was in response to abuses suffered by the former colonists under British rule. In colonial days even low ranking officers of The Crown could and did seize ALL the weapons in a town or village. The officer didn't need to get permission from or even inform his superiors. Those whose weapons were seized had no way to appeal and were never compensated for their loss of property.
Those who seized the weapons often sold them and pocketed the money.
Often they "clinched the sale" by including the information that thus&so town was currently without weapons and could be safely attacked by the pirates, outlaws, or Indians to whom the guns were sold.
Sometimes the soldiers would attack the town themselves, disguised as pirates, outlaws, or Indians, looting, murdering, raping, burning the town. And THEN sell the guns to pirates, outlaws, or Indians.
This inspired the former colonists to demand certain guarantees from their new United States government, including but not limited to:
People will be justly compensated when government seizes their property.
There must be due process and an appeal process for government seizure of private property; government official can't confiscate your stuff and assume personal ownership.
Towns and villages have the right to maintain arsenals and other defenses against attacks by pirates, outlaws, Indians, etc.
Keep in mind that those days when "ammo" meant lead for shot and kegs of gunpowder, it was very much PUBLIC business how and where powder was stored. The idea of some individual "right" to keep powder in a way that significantly increased risk to public safety would have inspired amazed laughter.