Quote History Quoted:
https://youtu.be/5FDOXK2p0N0
Might want to try this technique that's recommended by IWI for gas suppression.
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He's right, in that the gas in the face is coming from the piston system. A spring won't change that.
I have to disagree with the video, though. Sealing the small gap hidden under the rail may take a little more effort. However, it is cheaper, out of the way, and you never have to worry about removing it, forgetting to replace it, etc. Putting a rail cover on there would be in my way.
Also, his claim about the sealant making it hard to take the rifle apart is WAY overstated. The gap that needs to be filled is between the metal of the rifle and the polymer body that is wrapped around it. It's not like we are doing TI level tear downs on our rifles every month or something. Even if you do have to take it apart, it doesn't bond the parts together as bad as he makes it sound (unless you're silly enough to use epoxy or something like that). Most people use RTV silicone, "liquid gasket", etc. I used liquid electrical tape, myself. Any of those will pull away without much extra effort, and peels/scrapes off in just a few seconds.
It doesn't take much, either. I didn't take pics when I did mine, but it's a really small slot. Smaller than a coin slot in a vending machine. Once you put the rail back on over it, no one will even know it's there.