There is really no spec for side to side slop as long as the timing is ok (checked by looking down the barrel while cocking the hammer with a flashlight behind the cylinder, you look to see that the cylinder lines up with the barrel).
The more important issues are barrel to cylinder gap and end shake. End shake is the front to back slop. With the cylinder pushed all the way forward you want no more than about .008 to .010 at the max between the barrel and cylinder, .005 to .006 is ideal.
You then push the barrel to the rear and measure again, the difference is your end shake, you want this to be .005 or less.
So if forward you get .006 and back you get .009 you have .003 of end shake.
Now most of the revolver check out guides say "full lockup" (when the cylinder is at it tightest) is with the hammer down and the trigger held back, this is only correct for Colt Revolvers, Smith, Taurus etc are at full lockup with the hammer back.
I am sure there will be many that disagree with me on the full lockup and that's fine, I have been over it many times and have it from a guy who knows his stuff and it just makes sense when looking at it.
Here is the post that cleared things up for me:
Again, HOLDING THE TRIGGER BACK IS NOT A VALID TEST FOR ANYTHING ON ANY REVOLVERS EXCEPT THE OLDER COLT'S.
Almost all revolvers are locked up by the SIDE of the hand that rotates the cylinder pressing on the ejector ratchet.
When the action is cocked the top of the hand starts the cylinder rotating, but immediately bypasses the ejector ratchet and it's the SIDE of the hand that pushes the cylinder the rest of the way.
Once the hammer is just cocked, that's as tight as the cylinder is capable of locking.
Holding the trigger back cannot lock it any tighter since the side of the hand just slides past the ratchet.
No matter HOW hard you pull the trigger, the cylinder can't lock any tighter.
Again, no matter how tight it SEEMS to be locked, there's enough backlash designed into the action to allow the cylinder to move enough to align the chamber with the bore.
Only the older Colt's like the Python action locks up tight with the trigger pulled.
In the old Colt's the TOP of the hand pushes against the ejector ratchet to force the cylinder into tight Colt's "Bank Vault" lockup.
The harder you pull the trigger (within reason, you can damage it) the harder the hand pushes against the ratchet and the tighter the cylinder locks.
In guns like the S&W, Ruger, Dan Wesson and newer models of Colt's if the action is out of time and the cylinder isn't locking fully, you fit a WIDER hand.
In the old Colt's like the Python, if the action is out of time and the cylinder isn't locking fully, you either stretch the hand or fit a new LONGER hand.