We don't know if going to the gun range was a family activity when the Lanza's were still married. We don't know for sure if Nancy or Peter ever took Adam to the gun range. We don't know if the Lanza's went hunting together or if they were even hunters. We don't know more than we do know; this causing endless speculation. Studies have proven that the public remembers the first reporting of events more than the public remembers the true facts that come out with the patience of time.
It appears they had not been living together since 2001.
Nancy bought most or all of those guns, the ones Adam had or gained access to, in the last 2-3 years. I believe some or all of that has been verified as to dates purchased. I fail to see how hunting, going to the gun range, or a host of other things directly has to do with access in the home of these types of weapons. Access to guns that I doubt Adam could have purchased? Access to guns that went beyond a regular old rifle.
This may sound callous, but I'm not so sure in the scheme of thing that initial reporting remaining in people's minds about NL is the most important thing on everyone's minds. I don't think most people care about the blame as much as learning from the situation and preventing this the next time. Most people realize the news does a lot of misreporting in this day and age.