I was given a can of older GOEX FFg in the red, oval can 8 yrs. ago and wondered how it compared to the fresh batch of the same powder that I had. I loaded 70gr. of each in my .45-70 (Marlin #336, 22" Microgroove bbl.) with a Lyman #457124 cast bullet (sized to .458"*, 2.67" OAL) and ignited by a Win. large rifle magnum primer. Accuracy was the same for both powders, but not velocity:
70gr. Old Goex FFg = 1,151fps +-20fps;
70gr. New Goex FFg = 1,216fps +-30fps
UnfortunatelyI never repeated the test and didn't analyze the results statistically to determine whether those were chance variations or significant differences between the powders. What say ye, do lot to lot differences in GOEX or other brands of powder vary that much?
*I now size to .459" as accuracy is a bit better.