Very clearly, the change-over to the high speed hammer began first. Here's the story.
To begin with, I'm talking only about the M&P fixed sight revolver. I cannot speak with any authority about the target K frames.
1. The first
production M&P with the short action was S990184. This is clearly stated in Hellstrom's notes. It
shipped on April 7, 1948, so it had to have been assembled before that (I believe sometime in March, 1948).
2. There was at least one pre-production example, also according to Hellstrom's notes. It was put together clear back in October, 1947 (I assume in the tool room). It seems obvious the engineers were working on the hammer improvement for quite a while before it went into production.
3. Above S991315, I find
only one M&P with the long action (serial number S996765). It shipped in June, 1948. Every example I've found between those two numbers and above S996765 has the high speed hammer (except the odd .32 examples, mentioned in my previous post).
4. Revolver number C1 was
assembled on March 22, 1948. I don't have a ship date for it. It, of course, has the high speed hammer, but a one-line address.
5. All C prefix guns have the short action, but not all of them have the four line address (although most do). I have never seen an S prefix gun that has the four line address. (
Ooops! Mistake. I just went through the database again and found an exception. C58672 has the long action. It shipped on April 20, 1949, and has a 2" barrel. It is clearly an oddball, but at least one exists.)
6. Most of the S prefix guns had shipped by August, 1948. I have found only one that shipped later, and it left the factory in August,
1949! Clearly it got lost in the vault.
7. C prefix guns had been shipping for quite a while by August, 1948, and the vast majority of them had the four line address.
The preponderance of evidence leads to the conclusion that the switch to the high speed action was well under way before management decided to add three lines to the address on the frame.
There definitely are guns with the one line address and the high speed hammer - a few of them live in my safe.
Conversely, there are not many four line guns with the long action; at least I've only located one (see note 5 above). Other exceptions might be guns that went back to the service department for work and had the new address put on them; a practice that Roy had to stop.
I hope this post clears up some things for you and others.