It is a very good powder in the 35 Whelen. I believe it can be considered the first "short cut" powder, as it had the shortest grain in the original family of IMR powders.
I think one of the 2006 issues of Handloader had a write up on 4320.


Imagine your grave on a windy winter night. You've been dead for 70 years.
It's been 50 since a visitor last paused at your tombstone.....
Now explain why you're in a pissy mood today.