aren't shotguns like incredibly deadly in a home invasion situation
getting shot by 1 bullet of a military grade rifle is probably different than getting hundreds of pellets shot into you
Not exactly, bullets do not have magic killing properties. All a bullet is, is just a hunk of flying metal that damages organs by passing through them. Think of vital organs like a Heart or lung, even the brain. Also picture the bullet as an arrow from a bow or a knife. Some penetrate better than others, some do more damage than others. It depends of strength of the powder in the casing, the mass of the projectile, the speed at which it travels, and how it passes through a target.
This Mini-14 here:

fires the same type of ammunition as this M4 Carbine here:

One is made for civilian use, the other is made for military. They are both deadly. So basically as long as you can hit your target and strike an organ, you can kill just about everything.