The new ROCK ISLAND XT .22 is made of 4140 steel, not to be compared to Zamak guns which is what we used to call pot metal.
Nowadays zinc is considered "Gun metal" by dishonest manufacturers.
I have CNC produced 416 stainless triggers to replace the plastic triggers on Colt Mustangs, Mustang Plus II's, MK IV Government .380's and Sig P-238's. Video on installation in Sig;http://www.youtube.com/watch?v=Jh2v_-87DRM
Also I made up a hundred Llama .32 and .380 recoil spring buttons, checkered nicely and blued.