Super Redhawk's rear sight assembly problem?

[naphtali]

I was shooting one of my SRH 480s, and FA 83 475s yesterday with new 400-grain bullet loads @ 1150 fps. The SRH's inaccuracy was as disturbing as the M83's was encouraging.

1. With rear sight as low as I can set it, revolver shoots about 8 inches high at 25 yards and about 4 inches right of point of aim. The grouping was, charitably, about 6 inches per cylinderful.

2. SRH's rear sight assembly is wiggly laterally by hand. I strongly suspect this is the heart of the grouping problem. But if I use the elevation screw to increase tension -- reducing lateral movement of sight's base -- the point of impact problem becomes worse.
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With same bullet at similar 1150 fps 475 Linebaugh loading, the M83 was about 1 inch high at 25 yards and about 2 inches right of point of aim. Group was about 1.5 inches at 25 yards. This revolver was fired after the SRH, so I suspect I'll shoot better with it (first) today.
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I deduce the problem is less with me than the SRH. What is its problem? What can I do about it?

[Aggie01]

Stage 1:
Remove the rear sight, put it upside down on a hard surface and use a steel punch to peen the bottom edges to make it better fill the channel.

Stage 2:
Call H. Bowen and get one of his rear sights.

[AxeHandle]

Never have been a fan of the stock Ruger rear sight.... IMHO on my SRH set the Bowen Target is a wonderful fix...