Having built and shot the 408, I fail to see how the fellow in the video is able to keep a straight face with his pitch.
The 408 is much like the hype that Remington passed on about the 300RUM when it was first offered. Unfortunately what they claim and reality are totally different.
The cost of shooting 408 is as high if not more so than 50, due to the fact that only 1 company makes brass and only 1 company makes 408 bullets, so the costs are artificially high. True it uses less powder and standard primers, but this is more than offset by the major components higher cost.
The 750gr Amax bullets have a posted ( by Sierra) B.C. of 1.05, which greatly eclipses the .96 of the 408.
For the most part physics says that heavier bullets retain veloicty and retained energy longer than lighter 1s do. I believe with high BC bullets of similar design but different weights this holds true.
My own personal 50 shoots 750 gr Amaxs out of the 35.5" barrel at 3015 fps at the muzzle, according to Sierras Infinity 5.1 program the bullet is still traveling at 1171 fps at 3000 yards, which last I saw was still supersonic.
The 408 is a nice little ,in between cartridge, but for anyone to state it is superior ballistically to the 50, I think is sadly mistaken.
I see some promise in the 416 Barrett, but again it suffers from the same basic problems of proprietary components, at least at this time. I plan to build 1 as soon as a barrel arrives, to see if we are again being exagerated to.