Actually, some D.A. revolvers don't fully lock until the hammer has been released by the trigger and is nearly at the point where it has struck the firing pin (in the case of a frame mounted firing pin) or is nearly "home" (in the case of a hammer mounted firing pin).
A small amount of sideplay is normal in S&W and Ruger D.A. and some Colt revolvers, it should be almost or entirely absent in Colt D, E, and I frame revolvers.
Bob