I got it out this morning.
I stuck a fresh pencil in the bore and rammed the gun into the side of a sturdy metal table, which loosened it up and allowed me to retract the slide. However, when I picked the jammed cartridge up off the floor, I noticed something funny about it; it was a 9x18 Makarov.
I have no idea how I mixed it up, or how I did not notice the difference when I was chambering the round, but that's the whole cause of the jam; my stupidity. At least that returned my confidence to the P5 (I now just have somewhat lesser confidence in my own intelligence).
I have never had any problems with it up to this point and it by far has to be my favorite 9x19 pistol. I love the ergonomics, style, design, mag release, single stack mag, DA/SA trigger, everything.
I'm sure glad I sold off my plastic Glock 17 in order to trade up to this.
Zach