ITT: A bunch of people who only know guns from CoD and think buckshot only works at 30 yards and slugs at 100. For one, he's definitely using slugs, he even mentions exactly which in the 2nd chapter, Copper Sabot, even the pricing on them is pretty close to as mentioned in the chapter. There is a 0% chance that you use those types of rounds in a smooth-bore gun, as they would end up flipping around and hitting sideways and have a big spread even at 50y. So he's definitely using rifled. Those rounds, rifled, can easily hit 200y with 4 inch groups.
He uses shot vs. the wolves, which given the range he's fighting them at is fine, even if you do get a really gross spread shooting shot out of a rifled shotgun (the idea shooting shot out of rifled does any more damage than shooting slugs is a myth).
BTW, 00 buckshot can penetrate ballistic gel 9 inches deep at 100 yards. It'll be all over the place, but it's far from useless.
Also, overall 3-9x and 4-12x are the two most common choices for variable magnification scopes intended for 200-yard ranges. The one he's using looks more like a 4-12x.
In short, the author of this knows 10x more about guns than everyone trying to go hard on him trying to show off their PUBG/CoD knowledge.