Interested in small arms history? Make sure to pre-order a copy of my book, Chassepot to FAMAS: French Military Rifles 1866 - 2016: https://www.kickstarter.com/projects/headstamp/chassepot-to-famas-french-military-rifles-1866-201?ref=9kqy9c Direct gas impingement is an operating system that has been used only in a few production guns (all of them rifles). It is extremely simple, although perhaps not well suited to adjustability. It is also not the operating system of the AR series of rifles - we will cover those in a separate video next month. http://www.patreon.com/ForgottenWeapons Cool Forgotten Weapons merch! http://shop.bbtv.com/collections/forgotten-weapons Contact: Forgotten Weapons PO Box 87647 Tucson, AZ 85754