Mossberg makes a .223, threaded barrel bolt action, which also accepts AR magazines. Their website indicates that a model without iron sights is available.
Personally, I like the idea of iron sights. It's nice to have some sort of back-up in case your scope gets damaged.
I don't know how good the mossberg is, but gun test magazine reviewed a mossberg bolt action in the feb 13 issue and gave it an A- rating.