I agree Winchester 284 Win brass is hard to find. But that is only one brand of 284 Win brass and its quality is fair. One issue that is often encountered is varying neck wall thicknesses case to case and neck wall thickness varying around the diameter of a single case. These cases also have a relatively short primer pocket life.
There are two ways to get very high quality 284 brass.
1) Norma now makes it for Bullets.com with advanced production methods .
Read this and you will understand this is some very special brass:
Norma to Make 6mm Dasher and .284 Win Brass for Bullets.com « Daily Bulletin
If I were building a new 284 win today I would use this Norma brass.
The Norma brass in currently on sale here:
Bullets.com®
2) buy 6.5-284 Lapua brass and neck it up.
There are two ways to get very high quality 284 brass.
1) Norma now makes it for Bullets.com with advanced production methods .
Read this and you will understand this is some very special brass:
Norma to Make 6mm Dasher and .284 Win Brass for Bullets.com « Daily Bulletin
If I were building a new 284 win today I would use this Norma brass.
The Norma brass in currently on sale here:
Bullets.com®
2) buy 6.5-284 Lapua brass and neck it up.