4320 is a wonderful powder, much neglected. But, IMHO it is, in 4 out of 5 burn rate charts, misplaced. Not deliberately, not carelessly, just a function of it's unique chemistry. 4320 gets a rapidly faster burn as bullet weight goes up, as internal volume decreases, and as throat length diminishes. And when it gets near peak operating pressure the pressures rise steeply in relation to charge weight increases. I suggest anyone doing unpublished load development to use the Norma Burn Rate chart, which correctly places 4320 down between 3031 and 4895 rather than up with H380. Norma also has the added advantage of using a 2 number ratio of velocity vs pressure...the best burn chart in the industry IMO.
On your suggestion, I printed a copy of the Norma Burn Rate Chart. It does show some differences.
JB has long written than burn rates can vary from application to application.
Thnaks for that info. Not sure how fully I understand their Relative Velocity and Relative Pressure, but understand they're working against a standard, 43.2 gr. IMR 4350 in a .308 with 143 gr. FMJ bullet. I'm thinking about it.
DF
