watched a fun review by hickock45 on the new model 19 versus an older one.
Hickock45 was very passionate in his hate of the safety lock, its a genuine pain to have, however in a side by side comparison, the safety lock necessitated a change in the frame around the hammer.
The change reduced the nice curve of the frame, and put more metal in it. It hides most of the hammer now below the spur. With that change, and the change eliminating the flat cut on the forcing cone, does this mean a true increase in strength/durability has happened to the basic frame of the K series?