I was in the same boat a few years ago when I first moved to Colorado. I started off hunting elk in northwest Colorado on public land, and have since added deer tags when I draw them. I haven't hunted the plains. Too much private land, I worry about being legal. But to be more specific to your question, most of the public land (BLM, National Forest, State Land) is legal for centerfires. I have not hunted the State Wildlife areas a lot, but the ones I have hunted allowed centerfires. Grab a 2018 hunting regs brochure from Walmart or Dick's Sporting Goods. Most of the information about seasons, what is legal for a particular unit etc is in there. Or just read up on
https://cpw.state.co.us/. That should keep you legal. And I have called CPW before, they were very helpful and nice. Otherwise, pick an area you would like to hunt and go for it. 👍
