best sprinklers for well water?

Setting up a yard irrigaition system on my iron rich well. Its only 20ft. The sprinkler heads I've used get frozen all the time due to mineral deposits. Any rainbird models better for iron rich water?
thanks!

I have been using Rainbird 5000 series and 3500 series rotors on a well with 12-15ppm iron. I have 25 5000 rotors and 13 3500 rotors. I usually end up with one 5000 rotor at the beginning of each year that I have to replace, and its usually due to the wiper failing. But they have been working other than that.

-rick

My preference is Hunter heads but what do I know, some people prefer Chevrolets over Fords! Iron can be a problem on any sprinkler heads. http://www.proproducts.com/Default.aspx has a product called "Rid-0-Rust". It's a chemical that is injected with the sprinkler water to prevent the oxidation of iron. But it's expensive.