[DonVoigt]

Does the picture have anything to do with the question?

Other than it is a stock iron with screw?

Is the Iron still in place on the stock, with the screw in place- except head is broken off?

Then only chance is to drill the threaded end with a carbide drill, using a millng machine and remove the just out to the threads, then tap the screw body out the other way.

Clean out the threads or re tap to the original size.

A tricky and delicate procedure, IMO.