Not that 200 rounds is much of an experiment, but my rifle ran it flawlessly. And afterwards, it ran brass just fine (with no cleaning), which is kind of a no-no to run brass after steel w/o cleaning.
This was Brown Bear and then Geco.
I think steel case is mostly a problem in shorter gas rifles. Rifle length seems to help. I'd think twice before running steel in a 14.5" or shorter carbine gas rifle or pistol.
Not trying to hijack the thread, but do you like the Geco ammo? I bought a bunch, then heard it wasn't that good. I haven't had any problems with it.