auto/semi-auto weapon behavior after squib-fire?

Inspired by this image, purportedly of a machine gun barrel after a squib-load (and half a dozen rounds fired in behind it). It’s not clear whether the weapon finally stopped working, or the operator noticed something was wrong and released the trigger.

Question: how does an automatic or semiautomatic weapon behave when firing the rounds after the squib-load? Presumably there’s no recoil, since the obstructed barrel stops each bullet immediately after it gets fired. Presumably there’s also a massive blast of gas each time the slide comes back to eject the brass, since all of the propellant gas must now exit via the breech.

I get that the barrel can rupture under some circumstances, although it appears not to have done so in the above-linked image.

What else?

Here are a couple of examples with an M-16 from youtube:

And one with a Tommy gun:

https://www.youtube.com/watch?v=Nn4cgF_Sr3w

[quote=“engineer_comp_geek, post:2, topic:668970”]

Here are a couple of examples with an M-16 from youtube:

And one with a Tommy gun:
[/QUOTE]

The first and last videos show the barrel rupturing on the follow-up shot. The middle one isn’t so certain, though the caption does refer to the weapon exploding.

I’m more interested in how the weapon behaves when the barrel doesn’t rupture.