I saw this
thread a while ago that I brought back to life, but for those not subscribed to it:
I finally found it! I read this book
Grunts! by Mary Gentle a long time ago. I could never remember the name because it is a little silly. It chronicles the boss of an Orc warband in a Fantasy world that uncovers a stash of modern weapons and the portals to other worlds, including our own, in a dragon's lair. They proceed to begin an arms race with the elves and even recruit a circa 1980s United States Marine to teach them tactics and they grow into a modern fighting force when an insect race shows up to eat everybody, This is in no way a Warhammer Fantasy or
40K book, but it does show the progression of Feral Orks to Mechanized, and is pretty funny in a few spots. Plus, I think it is the only Orc centered-book I have ever read.