I going to guess the pressure difference between the .357 mag and the .44-40 is because the .44-40 case is prone to split under higher pressures. Just a guess, but I've shot alot of reloaded .44-40 and they do split rather easily.

"All that the South has ever desired was that the Union, as established by our forefathers, should be preserved, and that the government, as originally organized, should be administered in purity and truth." – Robert E. Lee