[producer]

This thread was a lifesaver - I had jam on a PM9 as described, discovered this thread and solved it with the technique mentioned.

Since I've disassembled the PM9 (and similar Browning-type, cam-locking barrel actions) many times, I couldn't understand what happened - then I examined the slide assembly and it dawned on me:

There are two slide cutouts on the left side of the slide. The rearmost one is the take-down cutout (for pushing out the Slide Lock), the second (toward the barrel end) its the slide lock cutout itself (for use with the Slide Lock to lock the slide back.

If you re-assemble and are not paying attention - you can push the slide all the way back and use the slide lock cutout for reassembly (meaning that you push the Slide Lock tab back in through that cutout), at which point the pin for the slide lock is in front of the barrel cam lug and the jam occurs.

So - moral of the story - pay attention during re-assembly.

Many thanks to Steve M1911A1 for the tip.