Yes as others have said, get a standard caliber. I have had several Colt AR-15 H-Bars and I can’t think of much better rifle period. They have a 1-7 twist so will handle the heavy bullets in 5.56. They will also shoot the lighter bullets OK.
If I am in a situation where I need a semi-auto, and it could happen, I am in a bad way, probably not going to make it out.
Maybe not for you but I personally would get a bolt action in .308 or 30-06. Remington is hard to beat but there are plenty of others. I would insist on way better than average accuracy. If the gun will not shoot 1 moa or better, I would see if it could be improved. If not trade it and start all over.
There are also plenty of good scopes. For the money the Nikons are unbeatable. You will never go wrong with a Leupold.
Also everyone should have a Ruger 10-22. Not that it is any better than others but it is reliable and there are plenty of high capacity mags for it.
Remington 700 or 770 in .308 or 30-06 married with a Leupold Mark IV will enable you to whack anything @ 600-800 yrds.
Still expensive but and more scope than gun but, if you want to keep bad people at bay and ducking.....