"Conjecture regarding the ability of the Model 19 to handle a steady diet of heavy .357 Mag. ammunition precipitated the development of the L-frame—a slightly larger and heavier frame and cylinder retaining the grip frame dimensions of the K-frame in 1981." -American Rifleman
https://www.americanrifleman.org/con...sson-model-19/
And a well written article on precisely this subject....
https://www.gunblast.com/Butch_MagnumLoads.htm