The old foster style slugs were a decent round out to 50 yards but without sights accuracy was not the best. With the advent of saboted slugs and newer higher-performance powders shotgun slugs have taken a serious upwards turn in ballistics terminal performance and in accuracy out to and over 150 yards. Decent optics, like those on rifles, will go a long ways in getting today’s rifled barreled guns doing much of what common deer rifles can do at 150 yards or even more.
Ask those who hunt the newer bolt guns with fully rifled pipes in both twenty and twelve gauges what they see delivered from the guns and ammunition both on paper and on animals like deer and bear. The effects of a hollow point, jacketed pistol bullet torqueing out at the 1700-1900 + velocities of todays sabots on a deer or bear are eye opening while some of todays screaming meemies rifle rounds pencil hole thru a deer with little expansion only to see the deer run off with little or no blood.
If you have no first hand experience on deer or bear with the slugs of today and the guns/scopes that round out the package, don’t make idle assumptions.
And on the same page as shotgun slugs are today’s muzzleloaders. They shoot high end pistol bullets well into the 2100 fps arena in 50 cal guns with moa accuracy at 100 yards and beyond. The only center-fire gun I need aside from a shotgun is a varmint caliber gun and inside of 200 yards my .45 cal inline blowing a 195 grain copper bullet out the muzzle in the neighborhood of 2200 fps will turn a coyote to mush at 150 yards and drops a deer right on the spot of impact.
If anything, center fire rifles are over rated.