^Yup. I'd still be shooting inexpensive Russian steel case, bi-metal jacket but the ranges near me banned it. I still have 500 rounds of it in reserve.
It's not solely the steel case that will add wear to your firearm. It's not the polymer coating on the cases that will induce malfunctions. Folks complain about steel case ammo wearing out extractors. Extractors are cheap and easy to replace.
It's a combination of the bi-metal jacketed projectile and the characteristics of the steel case that will accelerate the wear on a barrel. The projectile is mild steel jacket with a copper wash. Even though your barrel steel is harder than the bi-metal jacket, the bi-metal jacket is harder than copper. The steel case doesn't expand in the chamber like brass. Accelerated throat erosion. Somewhat increased flame cutting at the gas port.
I don't understand why people freak out about it. Almost everything on an AR is a wear item, including the barrel. It's meant to be eventually replaced. Spend more $$$ on brass case FMJ, get 1/3 to 1/2 more life out of your barrel. Spend less $$$ on Russian steel case bi-metal jacket, and the savings over brass will buy you a new barrel.
Brass case FMJ v.s. Russian Steel Case for plinking is a zero-sum proposition.
