12-02-2012, 05:41 AM
Using the IMI 7.62x39 brass, run a ladder test for pressure sensitivity in conjunction with a chonograph. Look for your first indication of pressure signs with erratic shifts in velocity, as you inspect your fired brass for bulge signs at the case web just above the extractor groove.
With the Grendel, I've seen a consistent relationship between velocity and charge weights across everyone's published data. A .2gr increase in the charge weight can be as much as 37fps. A .3gr increase can be 50-75fps, with a 75fps increase letting me know we're in a max load area.
Since your brass has less volume, you will build pressure faster. I think you really need to try CFE 223 from Hodgdon's. Do the math to get your charge weight relationship data for percentages to figure out a start load, and go from there. The CFE 223 is a high density, fine grain powder that might be just what you're looking for.
With the Grendel, I've seen a consistent relationship between velocity and charge weights across everyone's published data. A .2gr increase in the charge weight can be as much as 37fps. A .3gr increase can be 50-75fps, with a 75fps increase letting me know we're in a max load area.
Since your brass has less volume, you will build pressure faster. I think you really need to try CFE 223 from Hodgdon's. Do the math to get your charge weight relationship data for percentages to figure out a start load, and go from there. The CFE 223 is a high density, fine grain powder that might be just what you're looking for.
