a technique has been developed to generate precision round hole bores in composite structure railguns. development of tooling geometry, tool drive mechanism and coolant feed system has been successfully carried out. the combined techniques provide bores that are round and have better than 1.6 micrometers (63 microinches) surface finish throughout the 6 meter (20 foot) length and less than 25 mu m (0.001 inch) diameter runout. draw reaming with a pilot bushing is the method of machining. the bore is characterized first by comparison with a surface roughness gauge using a rigid bore scope and then by diameter measurement using air plugs/electronic gauging with subsequent digitized data collected on floppy discs. non-ferrous metals and plastic dielectric, including polycarbonate and fiberglass reinforced polyester have been cut. the resulting railguns have been successfully used for experiments conducted in a vacuum chamber pumped to less than 3 x 10 exp -6 torr pressure. (era citation 10: 028278)