In Uvalde, Texas, a gunman killed 19 children and two adults at an elementary school, after picking up two powerful, AR-15-style rifles ordered through an online seller shortly after his 18th birthday — something that would have also been perfectly legal in Pennsylvania. Here, over the last two years, more residents have been arming themselves than at any point in the last few decades or more. In Philadelphia, plagued by violent crime, firearm permit applications soared to likely the highest they’ve ever been. In the city, the number of licenses issued in 2021 spiked by more than 600%, with 52…