Meh, I call em' semi-automatic rifles.
The first successful semi-automatic weapon was the Mannlicher Model 85 invented in 1885. Semi-automatic weapons are not modern. In fact the Mannlicher Model 85 would truly be considered an antique firearm (its nearly 130 years old).
The MAIN differentiation between the Mannlicher Model 85 and the "modern sporting rifle" is the stock. The first references I can find to a pistol grip on a long arm are from a British Baker Cavalry gun from 1803. So pistol grips are even older than semi-automatic.
Hell even the AR-15 itself isn't "modern" its basic design was invented in 1957 (nearly 60 years ago). The reason the design is so popular is because its ergonomically correct for shooting, and the placement of the pistol grip allows you to balance the weight of a rifle better, making it easier to carry and shoot a firearm with a larger receiver and barrel.
The facts as I see them:
AR style weapons are not modern. (if cars are classics at 20 years, and antique at 25, and the individual parts and functions that make up the AR are all WELL over 100 years old, then the AR is not *MODERN* its easily a classic firearm design by now.)
ARs are not assault rifles.
Assault Weapon is a BS term, like MURDER GUN! meant to evoke an emotional response, not as an accurate reflection of the firearm itself.
Calling an AR or AK style firearm anything other than by their name, or by an accurate description of what they are feeds the nonsense. Modern Sporting Rifle is better than "Evil black kid killer gun" but on the whole playing the grabber's game isn't going to be what wins us this fight.