Up into the middle of the 20th century, the 2nd was seen as protecting the right to keep and bear arms, but specifically as protecting the right to keep and bear military style weapons. The short-barreled shotgun became restricted in the middle 1930s because it was argued that it had no military utility/wasn't used by the military (a false assertion, by the way) and therefore the 2nd didn't guarantee the right to own it.
It wasn't until after the Kennedy assassination that it began to be more common for people to suggest that guns should have a "sporting use" in order for them to be suitable for private ownership. That point of view clearly didn't come from anything in the constitution, nor from the founding fathers, nor even from previous rulings in U.S. court cases. It was, as far as I can tell, imported from Great Britain.