The steel case isn't so much the problem itself. It kinda compounds the problem. Steel doesn't expand and make a gas seal like brass does, so you tend to get a lot of burnt powder and other garbage that can blow back into the action. Mix that with some really dirty powder, and it can make a real mess of. The deal breaker for me is the bi-metal jacketed bullets. As super_hunt mentioned, its basically just copper washed steel. They are hard on rifling.

The other thing to consider about Tula is that it's literally the bottom of the barrel. Its not related to their handgun ammo, but there was a period when Tula was using super cheap powder in their .223 ammo. The powder created a bizarre pressure curve that, unless you were running it through a relatively over-gassed carbine, it would not cycle an AR.

I've never shot handguns enough to justify buying cheap ammo, but there was a period when I was burning through a lot of Wolf .223 in my AR's. Now that I'm older, wiser, and a lot less trigger happy, I've moved away from the cheap stuff and focused more on accuracy. The last case of Wolf ammo I bought is sitting in the back of a closet, waiting for a zombie apocalypse to start.