Abstract: The disclosure is directed to a process and a mill installation for the production of seamless tubes of high quality, in production mills having relatively modest production requirements. The mill installation comprises a cross roll piercing mill for piercing and initially elongating a solid cylindrical billet. Preferably, but not in all cases, the cross roll piercer is followed by a second cross roll "piercer" which functions purely as an elongator, and which functions to substantially elongate the pierced billet, typically in conjunction with an increase in O.D. and reduction in wall thickness. As a key feature, the pierced billet, previously processed by either one or two cross roll piercer/elongators, is thereafter further elongated by means of a Diescher-type elongator, and most particularly a novel form of such Diescher type elongator incorporating a restrained mandrel bar feature.