Does anyone have access to a list of the 7 who haven't co-signed?

These are the people to focus on with correspondence THANKING them for not jumping on the bandwagon.

A conciliatory tone would be good. Something like "We share your concerns about the (still rare, but) increasing frequency of true, random mass shootings (not to be confused with gang/drug activity, which is predictable criminal behavior). But we also believe that the proposed legistlation to enact a AWB, limit magazine capacity, and limit lawful, private sales, will not have the desired effect and will cause more problems and limit individual liberties beyond that which is envisioned. As such, thank you for your reasoned response in not co-sponsoring/endorsing this legislation."