The long gun thing didn't work out well for the Canadian grabbers. I think they finally gave up on it, when all those law-abiding subjects of the Crown blew them off.
The State wants to evaluate each and every portion of your life. The loophole that allows long guns to not be accounted for is long overdue. Plus one cannot confiscate that which is not known. Case in point: New Zealand.
They may well bring back the concept of the "arsenal tax" which was floated some years ago. They can't tax or confiscate what they don't know you own...so they have to know what you have and where you keep it...it supplies the probable cause for the search and seizure warrants down the road.
I also think it has to do with enhanced scrutiny and enhancing disqualifiers without needing legislation. If you look at the HQL it is being used to find non-disqualifying issues when looked at on the federal level, then twisting them to be something else under Maryland’s law when obtaining a HQL. People who already own firearms and were legally purchased are now becoming prohibited by filling out some paperwork and having to surrender their firearms.
I know a lot of hunters who have never purchased a handgun. Having the LQL will allow trying to dig up non-disqualifying issues in their past and then interpreting what they could be if it happened in MD. As Maryland increases the maximum sentence for common crimes (even though they typically give a mild sentence) it creates more prohibited people. They can also prohibit people who haven’t made a wrong choice for decades, by simply changing the maximum sentence in the law.