https://www.youtube.com/watch?v=UU9O1OimCpE https://bulkmunitions.com/5-56-vs-223-ammo-19-things-you-need-to-know/ https://exclusive.multibriefs.com/content/the-dangers-of-mixing-up-5.56x45mm-nato-and-.223-remington-rounds/recreation-leisure Personally, I purchase the least expensive 5.56 ammo available that has good quality, reloadable, brass. I was buying Lake City M855 seconds in loose 2,000 round boxes and never had any problems of any kind with any of them. I burn that up in training and then reload the spent brass as a kind of "Mk318 mod 0 clone" using Hogdons CFE 223 and 62 grain Barnes TSX https://www.hodgdonreloading.com/hodgdon/hodgdon-cfe-223 https://www.barnesbullets.com/product/tsx/?attribute_pa_bullet-diameter=0-224&attribute_pa_bullet-weight-gr=62&attribute_pa_bullet-type=tsx-bt&attribute_pa_rounds-per-box=50 On south Texas feral hogs it's not a "death ray", but it will do until the death ray gets here.