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Just a general question about imr4320. It is so close in burning rate to Varget. Some cartridges I load do not list imr 4320 but do list Varget, would it be safe to reduce the Varget loads by 10% and use them with IMR4320 (starting loads) of course to start with.
what calibers are you looking to load with the 4320, I'm sure some of the helpful members here will look through the manuals they have on hand for published data. I was gifted about 10# of 4320 some years back it was in little bags like you used to grind coffee into in the grocery stores. Just a plain bag with IMR 4320 stamped on the bag. I loaded a few 3006 to try went bang and grouped well so I loaded it. I have about 12 different manuals from different manufactures and time periods, as I just had surgery I can look for loads for the calibers you are looking to load.
4320 has data out there from 222 to 35 Whelen. What are you shooting? I would not transpose data.
Every burning rate chart I have ever seen warns against using it in loading - so I would say no. If you don't have data for such a well known powder you can assume there is a good reason for it.
6x55, 30-40 Krag, 257 roberts improved, 6x45, 30 apache, 45/70 , 7x57, 17 rem to name a few.
Burning rates are set by a set procedure. Powders burn differently at different pressure / volume levels. A powder that burns cleanly and efficient at 50,000 CUP may leave unburnt powder and heavy soot at 25,000 cup loads. Another may be fine at 25,000 cup and show pressure spikes at 60,000 in certain cartridges. Case volume also affects powder selection. I have seen several try to use IMR4831 in BP duplication loads with the above result of unburnt powder / soot. But it was a powder they had in large quantities on hand.
Find an older Lyman manual 45-47 or look at sites for on line manuals.
Data from DuPont 1997 for 4320 Max loads!
30-40 150gr 37.0 for 2420 fps
30-40 180gr 35.5 for 2210 fps
45-70 405gr 53.5 for 1720 fps
7x57 160gr 36.0 for 2295 fps
Warning! Double check with another source!
New lots may be made by another manufacturer and may differ markedly.
It would be easier to buy Varget.
I just went through the data for several different cartridges doing a comparison on the Hodgdon data site where both powders are used for the same bullet weight.
While similar, the data is enough different I would not trust it for a direct substitution.
The range of cartridges you intend to load, have large differences in capacity and pressure requirements. I suspect the powders will react differently under the different circumstances.
If you are only using starting load data, you probably could get away with it. I would not recommend it's use as a substitute at near full power data.
You never do direct substitution. You interpolated from a burn rate chart and start 20% low. Done it 100s of times no problems. 4320 is an odd ball powder that, unless you have a lot, has far better modern alternatives for which there is data.
I have a sealed can of Hi-Vel that is interesting but will stay sealed and on display.
BTW, there is no shortage of 4320 data on the Hodgdon website. Loads for over 50 w/4320.