It's kind of a pain, you have to unscrew and remove the pistol buffer rod then open the upper (I'm going to most likely replace the pistol buffer with a CAR tube and buffer to make this easier). This one has a "pull pin" style rear takedown pin that looks like an old grenade pin. You pull the pin, swing open the upper and load the mag, then close the upper and push the pin back in. Other than that, the gun functions just like a normal AR, bolt catch works as does the forward assist and charging handle. I've built several post-ban detachable mag pistols before and this is my first (and last thank you) fixed mag one.
BTW: the AR-15 is a big, loud .22 lr just like the pistols, so why do you bag on them?