Just because it's a no knock warrant don't the Leo's still need to identify themselves as police officers?
Who's to stop bad guys from yelling, "POLICE!! SEARCH WARRANT!!", before breaking down a door?
And personally, I don't believe someone yelling (in the midst of crashing through a solid door) "POLICE! SEARCH WARRANT!" constitutes "identifying yourself". Some home invaders have actually done that to disarm potential armed opposition from homeowners.
I don't care what you're wearing or what you yell. If you bust down my door you're catching a mag of 308 with your chest.
I have heard that's happened a few times during home invasions. BG's even dressed "SWAT-ish" to gain an edge. That's yet another reason the risk/reward of using them needs to be strictly evaluated. Several homeowners have been killed because they pulled a gun after hearing a crash in the middle of the night. PD had the wrong address. Oops.
A whole mag! 308!?