EDITED TO ADD: Please do not attempt this test unless you have a plastic or soft metal (aluminum or brass) rod. Also make sure you mark any deliberate squibs or disassemble them immediately.
I did finally get around to assembling 5 squibs in 9mm. I originally planned on making 5 more in .38 Special for a revolver demonstration, but I'll have to do those another day.
For this test I used 147gr coated bullets seated into an empty case with a live primer. I picked a S&W 5906 as the test gun simply because it was close at hand and a good representation of a tilting barrel action. When I fired the round, there was a muffled pop - about equivalent to that of a child's cap gun. No movement of the slide was seen, but faint wisps of smoke curled up from the rear of the slide.
Manually racking the slide (as would be done in a Tap, Rack, Bang) resulted in the now empty case being extracted and a fresh round loading part way into the chamber and jamming against the squibbed bullet now lodged just past the chamber. I attempted to clear the bullet using a plastic squib rod built for the purpose.
In all 5 test cases I was unable to remove the stuck bullet with hand pressure and had to drive out each bullet with the squib rod and several sharp blows from a mallet. This mirrors my past experiences with squibs and confirms that should a true no powder event occur "in the field", the gun would be effectively rendered inoperative.
The pictures below follow the number sequence that follows:
1. Gun after first squib. Notice it is still in battery.
2. Bullet stuck in the barrel (terrible pic notwithstanding)
3-4. New "live" cartridge after attempting to manually chamber a round from the magazine.
5-6. View showing the slide not in battery and the new cartridge sticking out of the chamber after allowing the slide to come forward using slide release.