Would it be a lot of trouble to change a Red Ramp front sight on a
Smith & Wesson model 66 and install a patridge like is on the blued
model 19 ?
The sight that's on the model 66 looks like it is machined into the
barrel and not pinned.
?????
The blued Model 19 has the same "Baugman" ramp front sight the Model 66 has, only the 66 usually has a red insert.
A Patridge sight is a post sight with a 90 degree rear vertical surface, and is preferred by target shooters.
If the sight is one that was forged in one piece with the barrel, the only way to replace the sight would be to have it machined off, a slot milled in the barrel ramp and a new sight pinned in place.
This is S&W's "Baugman" ramp front sight, so named for a famous FBI shooting instructor.
The Model 19 uses the same sight, sometimes with a red insert, early versions usually without the insert.