RE: 20 guage buckshot Vs. 100 pound hog
if you are gonna have to get a gun for him, I would go with the 16 ga.it doesn't kick as bad as most 20 ga. do and it has more knock down.
As for buckshot for hogs and deer , my wife and I hunted with nothing except shotguns with buckshot for about 20 years.many , many , many deer and hogs have fallen to the two of us. she shot a Rem. 100 in 16ga. with #1 buck.I shoot a 12 ga. with nothing except #4 buck.they work very well for us.my Mom and Dad also hunted with us and they use 12 ga. with #1 buck.
We all have taken over the years 100's of hogs up to and over 350 lbs.all with buckshot.not to mention the deer that we took.
that being said; ya may check and see if someone has a 16ga. and 20ga. you could try before you spend the $$$.
all this is just MHO. there may be some that disagrees with me on this ; but they are wrong. LOL just joking.
20 ga. with buckshot will take most hogs to 30 yards.