This video clip is from a marketing video made by H&K comparing the 10″ barreled HK 416 with the M4 when fired full of water, immediately after being submerged.
It is a pointless comparison. Obviously Stoner did not design the AR-15 platform to be fired waterlogged. If he had it would be piston driven. Still, it is interesting to see what happens.
I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!