Whenever Douglas supplied the barrels -- through the late 70s and early 80s I think -- they went into inventory and got used w/o relation to their actual date of manufacture.
Later Wilson barrels with a more checkered quality reputation might well have been used and shipped before all the Douglas barrels were.
In any event, they all bear no markings, so after Wilson became a supplier, no one can know for sure who made their barrel.
During that period, Ruger also bought and installed over 4000 Green Mountain barrels, which I've always found to be very good.
I've heard all sorts of reasons why Ruger did this, but the most believable is barrels were very difficult to procure in quantity at the time and Ruger took the best of what they could get.
I've had Wilson barrels on several different rifles and most of them shot very well, as long as they were installed properly.
One was a dog, it was slightly off center in the blank, and the bore diameter varied its entire length, similar to that mentioned by DH. Wilson wouldn't replace the barrel as they felt it was within their specified parameters. It wouldn't shoot anything well enough to be considered viable for hunting.
Most Wilson made barrels, used by Ruger were as good as the regular Douglas made barrels IMHO.
The chances of getting a bad Wilson barrel were very good though.
I don't know if Ruger only paid for lesser quality barrels to reduce costs or Wilson had to cut corners to keep up with the new production demands.
At the time, Wilson already had a tarnished quality reputation and that stigma stuck to Ruger to this day 50 years later.
Ruger No1 rifles can be a hunter's dream or nightmare.
