July 9, 2013January 20, 2009 The CMMG AR-15 Gas Piston Conversion Kit is available at Brownells. For more information on the CMMG AR-15 Gas Piston Conversion Kit visit Brownells. Share this gun video:Click to share on Facebook (Opens in new window)Click to share on Twitter (Opens in new window)Click to share on Pinterest (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Tumblr (Opens in new window)