There are many people who claim that the Second Amendment is useless for allowing a citizen militia to oppose a tyrannical government, because the US government of today has machine guns, tanks, warships, artillery, and fighter jets. They claim that no citizen militia could oppose a modern military armed with such weapons.
To me, this makes a good case for citizens owning bigger weapons, but even if this isn't your cup of tea, history doesn't support the belief that rifle armed militias can't oppose modern military forces. The Mexican government's response to the Zimmerman Telegram is a good example of this.
In the Zimmerman telegram, the German government proposed that Mexico should enter the war on the side of the Germans. This would have prevented the US from sending troops to Europe in opposition to Germany, and prevented the British from using Mexican oil to fuel their war machine. The Mexicans didn't feel that their military was up to the task, because they could not defeat the US military in the field, and even if they could, the Mexican military did not feel that they could control the large, primarily English-speaking population who were well supplied with guns and ammunition.
In short, a large group of citizens who are armed with personal weapons cannot be governed without their consent. It isn't as though the Mexican army was poorly equipped in those times, either. The German military had been supplying arms, advisors, and money to the Mexican military for over three years.
In fact, one single munitions ship, the SS Ypiranga, carried a large cargo of German ordinance to Mexico. The ship contained more than 15,000 cases of small arms ammunition, twenty heavy machine guns, and 250,000 rifles, in addition to other arms. In all, the ammunition and arms occupied 30 freight rail cars, and that was just one shipment.
German advisors were allegedly found at the scene of the battle of Nogales, and $12 million in military aid had been given to Mexico by the Germans in 1915. Twelve million dollars in 1915 is 272 million dollars today. This represents a fairly large sum for the time. In 1915, the US budget for the military was $426 million (1915 dollars), so the $12 million represented 3% of the US budget.