Originally Posted by Donald Paul

... hi everybody. Why do most folks refer to these anomalies as
cracks. These are actually FLAME CUTS caused by a very hot flame under extreme pressure {Think oxyacetylene torch, under very, very high pressure}. It will begin wherever gas leakage is
most likely, say at the forcing cone. {The top strap will suffer too}.
Once these hot gasses can find a way out, the leak will only grow and get worse. The 'K' frame is most at fault because of the thinner forcing cone at the six-o-clock location.
The lighter the projectile. the hotter the flame is behind the projectile. A heavier projectile uses up more of the flame prior to reaching the cylinder gap.
-Don