Are the 4006's that Calif Highway Patrol has new guns, or are they 10 yrs old pistols that S&W is just supplying parts for? I heard that if an agency orders enough of them, they'll pull the old 3rd Gen machines out of the mothballs and crank out a few.
The CHP reviewed their aging inventory of original 4006's, including the increasing numbers of required repairs as the guns were reaching and exceeding 20 years of service, and issued a memo outlining the need for new guns back in '06. (I came across a .pdf copy of that memo a few years ago.)
The replacement gun chosen was the current model of the 4006TSW. Initial (exhaustive) testing of the TSW version apparently made them expect the improved TSW models would provide even longer service than the original standard 3rd gen version.
S&W can make new versions of older models (which they've done, and can do for existing LE agency customers), but I've been told more than a few times that it's not done on old equipment.
I've been told that much of the older equipment on which the original 3rd gen guns were made has not only been taken out-of-service, but they got rid of it (not just put it out back).
That was one of the reasons there was continual improvement in the manufacturing of the 3rd gen guns, they were periodically introducing new methods and equipment. I was told just a few years ago that they had just opened a new barrel forging/manufacturing dept at the main plant. Then, later on when they moved production of the 3rd gen's to Houlton, it involved installing new equipment (and software) at the other plant.
I remember talking to one of the repair guys on the phone when I was calling to ask a couple questions a few years ago, before the new CHP contract was settled. He told me that the factory had run out of 4006 barrels (which are different than TSW barrels in more ways than just the loaded chamber inspection port).
He said that replacing a barrel for one of the old style CHP 4006's involved taking a TSW barrel and laboriously hand-filing the thicker barrel hood so it would fit & function in any specific old style 4006 slide. He said the last one he'd done had been a rather time consuming process.