From Michal on Patreon:
"Can you talk about difference between .223 Remington and 5.56 NATO? Or in more general terms about possibility of using military grade ammo in civilian rifles. I heard everything from 'it will explode' to 'it will work normally'."

The short answer is that the difference between .223 Remington and 5.56mm NATO is immaterial to most people. It's better the use .223 in .223 chambers in the long run, but really not a big deal. There is an excellent article on this written by Andrew Tuohy on the LuckyGunner blog which I can't link to in a YouTube description.

As for military grade ammunition, it is really no different than civilian packaged ammunition. Some folks with minimal firearms experience have the notion that commercial ammunition is somehow derated in quality or capability compared to military ammunition, and this is simply not true.