The Quackenbush guns are the top shelf in the air gun world. I own a much less expensive but still pricey Korean PCP rifle in .45 cal. I use .45 acp slugs cast in pure lead and bumped up to .457. It is a hoot to shoot, though less powerful than the Qbsh rifles at about 160 fpe.
I haven't shot it at 100 yards but it will hit what I aim at at 50, shooting offhand. Unfortunately, in the state where I live, air guns are illegal for hunting.
Pete