Comments on Contenders and WW-296 in the .357 mag
The original Contenders are not really as strong as the old literature supposes. Many people have stretched those thin frame sides and/or widened the hinge pin hole using very hot loads or powerful wildcats. The G2 is much stronger. the Encore is stronger, still.
And, the "wear" from hot loads in revolvers is more than just loosening parts by banging them around with the recoil. With high pressure comes high temperature, and with that comes forcing cone erosion. That is most likely the cause for the significant velocity loss that comes from shooting too many hot loads.
As for H-110/WW-296, in 1980, Winchester gave the max load in Winchester cases with Winchester magnum primers and an unspecified 158 grain jacketed bullet as 16.6 grains, with a pressure of 39,500 CUP and a velocity of 1610 fps from a 8-3/8" SAAMI test barrel. I don't think that load changed while Winchester was marketing 296. Their manual said to NOT REDUCE those loads at all, so that is what I shot. Hodgdon's 2006 load pamphlet gave 16.7 grains as max for H-110 under a 158 grain XTP, with a pressure of 40,700 CUP and a velocity of 1561 fps out of a 10" test barrel. Cases and primers were also Winchester. Both are well under the CUP standard of 46,000 CUP, but will be over the psi standard of 35,000 psi, although it is generally recognized that pressures measured in CUP with a copper crusher are numerically lower than if they had been measured in psi with a piezoelectric transducer. And, strangely, it is now OK to reduce those loads to reach the 35,000 psi standard, and to go even 3% below that.
Those velocities illustrate that it is hard to explain velocities in manuals. Both velocities are from the test barrels rather than from the same loads in a commercially available "example" revolver (as is often done to give more realistic velocity expectations), and neither barrel was vented. Yet the bigger load with the higher pressure gave a lower velocity from the longer barrel. Go figure!