and
Seriously...
![Shocked :shock:](./images/smilies/icon_eek.gif)
Someone who seems to know something about it commented below the video...
"...The rifle in question is chambered in a caliber called ".577 Tyranosaur", which as the name implies is just under 58/100 of an inch in bore. The round has muzzle energy similar to that of the .50 Browning Heavy Machinegun round. Rifles chambered for that round tend to weight something like 15kg or so to help with the recoil. The rifle in this video weights less than 6kg... "
Now that's a hell of a rifle!