How much adherence of the cartridge case to the chamber wall depends on the peak pressure, strength of the brass (thickness and anneal will affect this). That said, the toggle-link action is stronger than most people think. Take the sideplate off one of those rifles and note the line of backthrust runs straight through from the bolt to the shoulders of the receiver. (The rear link should contact the shoulder. Unfortunately, in some instances it does not, so the force is taken up by the pivot pin. The pin then takes the force in shear with some bending. If strong pins are in place, such as if the pins are hardened drillrod, the pin won't bend, nor shear.) The P08 Luger is a toggle-link action, and there was at least one rifle design of the same type that was chambered for .276, as was the original Garand, before Army Chief of Staff Douglas MacArthur ordered it chambered for .30-06. I'm not sure I would want to subject the "brass" framed guns to repeated highpressure loads due to possible deformation of the shoulders, but a steel receiver '73 should have no problems with .44 Mangle-em factory loads, IF Uberti guarrantees them for that level.