There is a protein % calculator on Metzer's site. You can use that to figure out how to mix to get the right % of protein.
You are going to need some sort of source for trace minerals. If there is really good grazing and plenty of bugs for the hens, they might do OK. Otherwise, you are probably going to see your egg production drop off.
There are a lot of grain products in commercial feed that I consider to be little better than floor sweepings.
I consider corn to be good feed, but it is very high calorie. It'll make your birds fat if you don't limit the amount that you use.