No, not by the production line but maybe a prior owner installed lighter springs and or stoned the parts. It is around 20 years old and a lot of use eventually smooths the parts the same as stoning them. I don't know what your comparison standard is but especially in production more recent than your 60-4 some trigger actions have been less than stellar.
BTW, I like 60-4s. I'm a little old fashioned in that I prefer to fire magnums in larger and heavier frames.
I've found 60-4s easy to fire very accurately with home cast bullets.[/QUOTE]
Ahem...they also shoot REALLY WELL with factory ammo!

My two have both thought they were K-38's when firing Speer's 125 grain JHP Plus P ammo. I now have the 135 grain Short Barrel load, which shoots about the same . These loads were outstanding, but various other factory loads also shoot very well.
These are very fine small .38's for general protection and trail use where you aren't likely to need more than .38 Special power.
I agree that this size gun is too small for .357 use. Recoil is apt to be too severe for most shooters. If you aren't careful, the hard recoil will also let the cylinder release cut your thumb. The Ruger SP-101 is the absolute smallest .357 I want. And not as a snub. The three-inch barrel is the logical choice, I believe. Ruger's cylinder release design precludes those nasty cuts to the shooter's thumb.
The actions of both of my M-60-4's are indeed pretty smooth, although mine were bought used. However, they had seen little or no use, and I don't think either had had an action job.
My 66-3, made in 1990 and bought new, also has a smooth action and wore-in very quickly. I think the early 1990's were just an especially good time for high QC.