I happen to work at YTC Range Control. What Bob said is correct. You need to fill out firearms registration with the DA police (don't bring the firearms) to register you will need make, model, barrel color, serial number, not sure what else as I have not registered any of mine. When the background check is complete you will then be allowed to bring the firearms onto base. You will need to purchase a Rec card for $25 at the gym after filling more paperwork and watching a video. You get a down range pass for your dash as Range Control located 6 miles up Firing Center Rd. from the main gate. You get to choose 3 open training areas to hunt and the open TA's change day to day depending on troop training.
There are lots of quail, huns, and chucker, don't shoot the sage grouse. You can also hunt coyote and cougar (there are at least 14 known cougar living on base). Couple of us at RC know where 3 are living and are just waiting for the first snow fall to follow tracks. They have been decimating the deer the last year as well as taken a few elk.