Hi, pvq,
Those would have been my assessments, but I figured you would find out for yourself. The 999 was the top of the H&R line but not really a target pistol. Main problem was not in the break top action, but in failure to get all the cylinder holes lined up, which destroys accuracy. When you luck out and come up clean with a range rod on all the chambers, the guns shoot pretty well. Of course, as you say, it is tough to do anything with the trigger, and I have tried. A screw through the trigger guard to reduce overtravel helps a surprising amount.
Hi, ddt4free,
The slop you mention is a factor of the cylinder lockup, which involves the cylinder bolt (stop), regardless of whether the gun is top break or swing out. It can increase with firing, but usually not significantly.
The other "slop" in a revolver is end shake, and it too has little to do with how the gun loads, except that in the topbreak strain and battering of the top strap lugs will eventually allow the cylinder to develop end shake. I have seen many top breaks which had so much looseness that the firing pin would not strike the primer unless the gun was held together at the time of firing. That does not happen with a sideswing revolver.
Jim