I was told a LONG time ago that anything above 1200 fps in a long barreled Sharps was a "balistically unstable" load.
Yea or Nea?
Sounds like another old wives' tale. 540 some gr slugs are pushed 1340's with slighly longer cases-- or the 2.1 throated long to accomodate more powder. They have no trouble getting good accuray to 1000 yds.
I could see some lot numbers of powders not being able to generate that speed and still produce that kinda accuracy though. I've run the Postell to 1300 otta a conventionally throated 45/70 with good accuracy albeit at short range--- using 3F. Readily admit though my accuracy loading is just under sound at 1095 making a solid moa.