It did not like the mud.

I suspect few guns do.  What was it he said at the end (8m:00s), something about being impressed with its performance?

Can somewhat confirm that most guns don't. Did a similar, but less formal, test with a friend once. I had an HK45CT, he a P226 in 40. Shooting next to a pond, found some silty mud next to it, both thought "screw it, they need to get cleaned afterwards anyways." plopped it down 3x on each side, just held a couple inches up and dropped flat, then tried to get through a whole mag.

HK did a bit better than the Sig, but having two top of the line handguns struggle pretty significantly really opened my eyes to just how nasty mud is for guns. Especially when it's finer silty mud (more like what he has there) vs chunky. It's the only time either of those guns ever failed.

Honestly, I was expecting the 5.7 to go all the way without a failure.

Pretty impressive imo.

Dude is a tool for worrying about a polymer firearm blowing up in his face.

I wonder what the outcome would be using SS198LF

It did very well! Very few guns have done better in that test.

I used to carry a FiveseveN before FN downloaded the ammo. If you still use one for self defense, I would feel very good about those results.

Most people may drop their gun in the mud, but very rarely will anyone ever submerge their gun and fully cover it with mud like he did in the final phase of the gauntlet test.    The sheer weight alone of all that mud coating the entire slide would make most guns not cycle.

I am very impressed with the FiveSeven's performance.  I did the first mud test perfectly.  It was only when it was all the test back to back without a rinse that caused it to finally have four stoppages.   That is still fantastic.