You can shoot on most federal land, (and state land here) unless it is close for some wierd reason.
You're best maps can be bought from the USGS
http://store.usgs.gov/b2c_usgs/b2c/s...itrex_prd)/.do
You can also get BLM maps at your BLM office and National Forest/Grass Land maps at your local forest service.
The maps you get localy are normaly 1:100,000 scale. You can get 1:24000 on line for about a dollar a sheet. These low scale maps are better for shooting (and hunting). Mainly because you can use them as a range finder.
Just get a 1:24000 protractor to go with your maps.
Best shooting on public land I've found are deserted gravel pits. (They should be located on the map).
There is one about 2 miles from my house that I can shoot 2000 yards or better. One thing I like about gravel pits is there is less vegitation meaning less chance of fires.