This BCA AR-15 Barrel is a 7.5" M4 contour barrel profile made of 4150 steel with a black nitride finish. It has a 1:7 twist rate and is chambered in 5.56 NATO. Finished Barrels go through a 100% Inspection Process. Inspections Equipment includes CMMs and Air Gauges for the Bores. {{widget type="Magento\Cms\Block\Widget\Block" template="widget/static_block/default.phtml" block_id="42"}} It is the responsibility of the consumer to ensure all state, local, federal, and ITAR regulations are followed Does not include gas block or gas tube