Back when Ferris Pindell was trying to make the 81's competitive, the .900 length jackets were problematic. High quality jackets on this long jacket were not concentric enough to win matches. A friend bought 240,000 jackets of .900 in length and ended up wasting time and money trying to win with them. The .825 jacket was very good, but there were problems in manufacturing the longer .900 jacket. He offered the me the whole lot for $24 per thousand, I had no need for them. He could not give the jackets away, 10 years later.
Jacket quality WAS a major issue.
I had a set of dies made for a 75g low drag BT bullet based on the .900 length jacket, what a disappointment. Gene Harwood was also neck deep in the .900 jacket issues as it had been a major stumbling block for a long time.
Gene designed a next generation of low drag which was a 6mm 85g low drag BT on a jacket longer than .900,
J4 had no interest. After Gene died, I sent the bullets to Sierra begging them to consider making them.
So, the issue of jacket uniformity and larger than PPC cases to push those longer bullets are another can of worms. Bart could probably comment on this issue, IF there is an issue today.