"I understand S&W and Ruger use different metal processes with accounts for part of the differences for the mass of a Ruger revolver."
----Bill
Answer: Negative. S&W M-29 adopts, fifty years later, a turn-of-the-century Model 1905 .44 Special to .44 Remington Magnum. Beefed up, better steel and heat treatment. The Redhawk was specifically designed around the .44 Mag, to survive continuous fire with full house loads. The S&W frame is drop forged and of "side plate" design. The Ruger is lost wax cast, and of "solid frame" construction, with modular trigger assembly. The S&W cylinder locks up vis a spring-loaded cylinder pin held in the standing breech, and at the front by a spring-loaded plunger in the extractor rod. The cylinder pin arrangement on the Smith limits thickness of the barrel socket in the frame. The Redhawk extractor rod is lower than the cylinder axis, making room for a thicker barrel socket. The Redhawk cylinder is latched via cylinder pin at the standing breech, and with a strong sliding latch securing yoke to frame.
"... can a Redhawk handle all the... heaviest of loads that Super Redhawk can?"
----Bill
Answer: Yes.
Loadwise, the RedHawk and SRH are equal. Frame, cylinder, yoke, all the same size. The Super Redhawk incorporates three features absent the Redhawk: 1) extractor shroud integral with the frame; 2) separate mainspring and trigger spring, which allows for a cleaner trigger job on the SRH; 3) grip spike on SRH provides mounting for a better variety of grips.
Because the SRH replaces the drop forged barrel of the Redhawk with round stock, machining is greatly reduced. And without the Redhawk's grip straps to finish and polish, the SRH grip spike saves additional labor. The Super Redhawk costs less to make, and is the better design for shootability.
David Bradshaw