The founders of the Constitution were intelligent enough NOT to limit the scope of the 2nd amendment. If they wanted to be specific the 2nd amendment would have said "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear single-shot Breech loaders, shall not be infringed.
Unfortunately for  you the founders of this great Constitution had the forethought to understand that innovation  is inevitable. Regardless of innovation our founding fathers understood that the citizens must secure the ability to maintain a free state in the event of  tyrannical government control over the will and freedoms of the people.
Last but not least a well regulated militia, well regulated means something is working well or in proper order. Militia is a military force raised by the civilian population in the event of an emergency, with a bit of training your family, neighbor or friend are members of your militia.