Dom sent in this link for those who want to up their game with their Gas Blowbacks. This Bay Area Airsofter video features a GHK M4 Devilhunter which is gas efficient... "Credit goes to Austin Wingler and David David on FB for helping me. This mod really changes the game for all my gbbrs! Skip to 9:00 if you want to just see the efficiency test. Sorry for rambling so much!"