I don't use Tula or any other steel cased ammo through my ARs, Wolf Gold runs fine with Sprinco Blue Spring and H2 buffer. It locks back on all the .223 ammo I've put through it including PMC Bronze but it has all been brass case. FYI, I just unpinned the FSP to install a C4 MLok rail so I pin gauged the gas port, it measured .076.