How are S&W barrels measured?

[cquickel]

Are S&W Model 10, 15, 19, 29 barrels measured from the end of the frame to the end of the muzzle or from the beginning of the cone to the end of the muzzle?

 

[cquickel]

Are S&W Model 10, 15, 19, 29 barrels measured from the end of the frame to the end of the muzzle or from the beginning of the cone to the end of the muzzle?

 

[diamonback68]

Measure from the face of the cylinder to the muzzle.