Tula made ammo is a love/hate relationship. Made in Russia with steel cases (but Wolf, another Russian maker, offers some brass cased loads), some claim that the steel cases may cause extraction problems or even damage the extractor, the cases may jam in the chamber (depending on the coating), and they are also very dirty (requires lots of Hoppe's). They also have steel core bullets which many indoor and some outdoor ranges prohibit. They are Berdan primed (not normally reloadable), but non-corrosive.
Generally, the polymer coated steel cases (a matte grey/brown finish) give the least extraction problems, as the polymer is slick, almost like Teflon. Some of the ammo is silver in color, which is zinc plated steel cases, which some say function well (but others hate), and the cheapest are lacquer painted steel cases, which may gum and stick in the chamber when they get hot.
If you shop around, there is some other brass cased .223/5.56 available, both new and reloaded (remanufactured using brass cases) that is very price competitive but without the disadvantages of the steel cases.
FYI many of the Russian designed weapons are designed for steel cased ammo and generally function very well with it, and may even prefer it!