Unless you are defending your home from outside, use a shotgun. Lightweight is an ar15, or a 10/22.

And shotguns do overpenatrate, shotguns have more recoil, less capacity, and are no where near as acurate, so you may hit someone or thing you care about, ar15's are highly customizable, incredibly acurate, AR15 hands down

Speer gold dot also makes a soft tip 223 that will mushroom and dump all its energy into a soft target and also get you an instant stop.
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The Federal Barnes tsx 223 is an extremely nasty deffesnive round as well, this is what I keep loaded un my home deffesne rifle, look up Balistics test of this round it hits as hard as bullets way above ots weight class and has almost no recoil
federalpremium.com/rifle/premium-centerfire-rifle/barnes-tsx/11-P223S.html-------

hornady.com/ammunition/rifle/223-remington-55-gr-critical-defense#!/
This is what most law enforcement uses in their ARS the only reason why the military doesn't use it is because NATO doesn't allow hollow points in combat

Ar15 on either 300 blackout or 556/223 either of these are EXCELLENT light weight home deffense weapons and they are light and not much recoil.
With the proper defensive ammo over penatration will not be an issue with an AR15, Hornady critical deffense 223 ammo is a great deffensive round that is a hollow point that won't over penatrate but will stop a threat lightning quick,