Very basic breakdown of Ruger barrels:
Douglas from '67-'73
Wilson from '73-'91
Ruger hammer-forged from '91-Current
Other contracts filled in where needed, if Wilson or Douglas couldn't meet demand.
The Wilson years earned a reputation for being all over the map for 'accuracy' and quality.
Wilson barrels, however, were only in use for a very short time in early production 77 Mk IIs. Their bad reputation was earned on the 77 'tang-safety'.
Once Ruger went to in-house production, quality only got better as time passed.
So, if you want to make sure you have the best odds at getting a good barrel, make sure it's a '92+ Mk II.
But, as ratshooter mentioned, not all of the barrels from 'bad' years were actually 'bad', either.
As I added in a previous discussion about 'tang-safety' vs Mk II Ruger 77s...
I have a 78 prefix tang-safety 77V that was originally chambered for .220 Swift. I have no idea whose barrel it was, but it shot like a dream (it was of ~1983 production, when several additional contractors are said to have supplied barrels). And that barrel, 4,500+ rounds later, is still going strong on another 78-prefix 77V tang-safety, in the hands of a predator control contractor in Montana.