There have been a lot of discussions of the SA Model 14's on this forum over the years. And in most of those discussions, we could rely on Ralph Tremaine to participate in said discussions. Here's what Ralph had to say:
"There are two ways to make a SAO K-38 from a double action K-38: One is to remove the double action sear. The other is to install the conversion kit.
How about if it's been altered with the conversion kit------but doesn't letter"? That's done by cocking the hammer and looking down at the front of the hammer. If it looks pretty much like a standard hammer without the D.A. sear, then that's what it is. If it doesn't look anything like a standard hammer, and there's no place to attach a D.A. sear, then it's a SAO hammer from a conversion kit (or it was born that way).
If you wouldn't know a D.A. hammer or a S.A.O. hammer from a bale of hay, then get a ruler of some sort. A machinist rule is best (easiest to use), but a yard stick will work. In the beginning, SINGLE ACTION ONLY K-38's were more properly known as SHORT ACTION SINGLE ACTION K-38's. So, get a regular, everyday K-38, cock the hammer, and measure from the tip of the firing pin to the rear of the rear sight housing-----1/2" right? Get your S.A. K-38 and measure the same thing. If it's less (I've forgotten how much less, and my SAO K-38 is long gone.), then you have a SHORT ACTION SINGLE ACTION K-38 made that way by the factory, or pretty much anybody else that knows which end of a screwdriver to hold onto."
Lots of folks suggest that simply removing the DA sear will get you a SAO revolver. That is true as far it goes. However, you must remember that the SAO hammer/trigger has a different geometry to it than the normal sa/da hammer/trigger. Also, keep in mind that the SA version was introduced for formal Bullseye competition, and there were a lot of very serious competitors who would do what it takes to gain the slightest advantage. With the SA parts installed, the hammer does not travel as far back as with the DA hammer, thus taking less time to cock the hammer. This in turn provides for a shorter travel for the hammer firing pin to strike the primer. Faster cocking time + quicker lock time = less wobble = better scores--at least theoretically. For the best shooters of the day, it likely did provide a slight advantage.
Here are a couple of pics showing the difference in a SA hammer vs a DA hammer at full cock. Note the SA hammer has less distance to travel to strike the primer.
This one also shows the physical difference between the two...SA on left, DA on right.
So by simply removing the DA sear, you have gained zero mechanical advantage.
As Jack stated, the ONLY way to tell if a SA Model 14 is factory or altered after the fact is a Letter of Authentication. S&W offered SA Trigger Kits that were drop-in, so they were easily converted to the Short Action Single Action, as Ralph stated.
I have a factory built Model 14-1 single action variation that was shipped June 28, 1961. It was in a shipment of two, both being the first factory shipped Single Action K-38 Masterpieces.
...Ben
