Most Steel cased ammo, especially .223 is safe to fire in all modern AR's. The problems arise from sustained fire with lacquer coated cases where the lacquer can melt and build up in the chamber along with carbon. This can create a failure to feed or a stuck case. I have fired steel case ammo in every one of my AR's (7 of them) for over 10 years. If you clean your weapon and are a safe shooter there should not be any problem. The naysayers are generally keyboard cowboy mall ninjas that read something somewhere and just pass on the rumor. There is bad ammo out there, in steel, brass and aluminum. Buy quality reputable ammo from known manufacturers and you should not ever have an issue.
I'm going to assume you mean steel case ammo. I don't work for or am affiliated in any way with Anderson Manufacturing other than being a proud owner of their products but to answer your question, no it doesn't do enough damage to warrant any worries. Steel case ammo has a bi-metal projectile that has a higher brinell hardness than brass case ammo leading to faster bore erosion, but unless you shoot thousands upon thousands of rounds you will never know
Yes but it's not recommended
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