The presses we have here has no issue with printing black. We run into prolbems sometimes when our chemical and plates are not so good.
If you want a rich black i suggest that you use C100 M100 Y100 K100.
Can't get darker than that.
It also depends on the press and pressman....he gotta get perfect registration.
so far i've heard of many different rich black combinations. the key is to saturate cmyk blacks just far enough without getting to much of an ink build. 100% across the board is heavy. 60, 40, 40, 100 sounds like it's pushing it enough.
Considering the type of stock the image is printed on is also a factor when designing using "Black".