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"Oxymoron?" You got the last part correct!

He's loving this -- uses relative adjectives for everything: fewer, more, less, some, etc. The degree to which his new laws would be effective have been proven false in reality. During the 10 year AWB 1994-2004, there was no measurable decrease -- or increase -- in overall gun violence due to the law. The downward trend in gun deaths was already begun before the ban, and it continued long after it was sunset. That fact while the number of AK and AR style weapons in the hands of the public increased dramatically. The AR is now the most prolific semi-auto sporting rifle in the US. People were still buying close-to-AR versions during the ban as the manufacturers made enough cosmetic changes to make them legal without impacting the function and lethality.
What makes a gun "more or less lethal?" I submit that the individual using it is the primary factor. A .38 special or .380 ACP in the hands of a well trained and practiced shooter can out perform a novice with a rifle if the scenario is a mass shooting. Before Mandalay Bay, the record for the most deaths in a mass shooting belonged to Virginia Tech in which 33 died (incl. the gunman) and 23 others injured 9though not all by gunfire). The weapons were a Glock 19 9mm and a Walther P22 .22LR -- both pistols!
There are also many more powerful rifles on the market and in owners' hands which are not considered assault weapons because they don't look the part. There are also non-assault-weapon versions of semi-auto rifles that are fine to own with anti-2A people, even though there's no real difference between those and the so-called AW.
The AR and AK variants are being attacked relentlessly for two reasons -- they look scary to the ignorant masses, and they have been drummed up as the choice of mass shooters because they are "more lethal". All firearms are lethal. Nothing makes the AR more lethal than other rifles of a similar category.
As for magazine restrictions, it's still possible to own 50 10-rd mags to have 500 rds at the ready, just like having 16 or 17 30-rd mags provides. The difference is you need to reload more often, but a rehearsed shooter can do a mag change in under 3 seconds.
The biggest problem with banning a gun believed to be 'more lethal" is that LE will never be able to stop the criminals from having them. When 9mm Uzis and pistols were becoming popular among gangs, the Cops still carried a revolver with 5-6 shots max. Eventually, LE adopted the semi-auto handguns so as to not be out-gunned by the criminals. Many also carry an AR-15 in their patrol vehicles for the same reason.
Whatever the police carry for protection, the public has the right to also carry, because the threats are the same.
By banning "more lethal rifles," you are necessarily depriving the law abiding of the most effective option for self defense, even though law enforcement use them -- including DC agents who carry them as PDWs (Personal defense Weapons).