I just gotta ask... why would you put a red dot on a Krieger barrel? Are you planning to shoot limited USPSA Rifle? If the cap has a notch in it that allows removal with out having to pass over the muzzle brake, then it is fine. If the cap does not have a notch then it will not fit over that brake and it will impair your ability to remove the handguard if the gas system needs servicing.
Only have it on to shoot tomorrow. And the barrel was a bonus. The price I got it for is like it was free. So I had to get it. B4 I seen it I was only building it to shoot at 300yards max. Now time to start doing hand loads and see what I can accurately shoot.