Sure there is a numbers difference between 223 and 5.56 but it doesn't make any real life difference. Completely safe to shoot factory 5.56 in a factory 223 marked barrel. With 10s of thousands of 5.56 and 223 ARs in the USA and with millions of rounds of both ammo flavors flowing freely it is amazing there are not daily kabooms and equally impressive everyone knows not to shoot 5.56 in a 223 chamber.
Any chance you can find some "compelling" evidence on the www that the moon landing was faked, UFOs are real, the govt killed Kennedy, ........?
