Some of the red area appears to be "flash or trees" from the forming process. The red stuff in the trigger well will have to be cut out.
There is no mill required with the polymer 80 lower as they furnish you with a jig and a hand drill and dremel tool will work just fine to finish the lower.
There is no mill required with the polymer 80 lower as they furnish you with a jig and a hand drill and dremel tool will work just fine to finish the lower.