The change was made at the beginng of 1980. With the way serial numbers are scattered all over the place place it'd just be a guess within a wide serial number range.
I have a 257 Roberts "B" 132-05XXX that shipped in Jan 1980. The 257 Roberts was first "cartaloged" in 1980 and the first run seems to be in the 130-05xxx serial range. So if we use that as the start/end point you could say 130-05xxx BUT the individual rifles could be plus or minus several thousand either way. But that would be a pretty good starting point.
The good thing about the trigger change is you can actually look at the trigger and know which it is. With the barrel change from Douglas to Wilson there is simply no way to know. I thought about actaully checking with a gas chromatigrapgh to see if they had a different alloy or trace elements but frankly it seemed like overkill and not something a guy could easily do to check, so why bother.
A BUNCH of #1s were first cataloged/available in the 1980 catalog. 223, 257 Roberts, 280 Rem as "B"s and a bunch of "V"s
I'm not sure where the 130-10000 comes from. That would certainly be a stretch in my view. There is simply no way to tell when the change took place by physically looking at the barrels.. I tend to use 130-05000 as the upper limit as to where you can be pretty sure that you are getting a Douglas barrel. Given the way rifles are assembled at the plant there well may be guns that are higher with Douglas barrels BUt I'd be uncertain that far out. I would sure check with records and get a ship date before I had any confidence past 130-05XXX.
Ross
The '78 date… seems to… confirm a Wilson barrel. FWIW, she will put three into 5/8" at 100Y. 
