That is the whole point. By eliminating the muzzle crack, all you get is the supersonic flight signature. This will give you conflicting reports from witnesses and usually mask the true capabilities of the shooter. If a shooter is really good, he can use the supersonic crack of the bullet to really do some psyche jobs on the people down range.
Mike
I read in the Wash Post today ....witnesses heard loud booms...like a car backfire.