The gas tube, also known as the direct impingement system, made internal durability unreliable. Almost any AR-15 rifle with the gas tube, including KAC rifles issued to British Army SOBs and Royal Marines, couldn’t fire after being submerged.

I found a YouTube link in your post. Here are links to the same video on alternative frontends that protect your privacy:

• yewtu.be
• inv.nadeko.net
• yt.artemislena.eu
• piped.video