The EZTUNE from BRT solves the problem of overported and overgassed rifles -- without adding complexity. This simple, drop-in solution just replaces your gas tube with a new tube that has a smaller port size. This slows how much gas enters the direct impingement system that affects carrier speed and gas blowback. If you got gas in the face from using a suppressor on a shorter barrel -- an EZTUNE gas tube is the simplest and most robust way to reduce gas blowback.
The EZTUNES are laser marked for quick identification. Select an EZTUNE for your gas system length (Car = Carbine, Mid = Midlength) and for your barrel length: Suppressed all lengths, 10-12" barrels, 12-14" barrels, and 14-16" barrels. The smaller diameter port on your gas tube will restrict the gas accordingly, slowing peak bolt carrier velocity. Note that you may experience some gas leak if you have a loose gas block to barrel fitment. You can test this by removing the cross pin and/or set screws to see if your gas block freely and loosely spins around the gas block journal. It is recommended you use a gas block with a slight interference fit (needs heat for installation) between your gas block and barrel, to ensure a better seal. If you experience leakage around the gas block, you'll want to be using a glove on your support hand if you find that support hand over the area of the gas block. Available Here