I cracked open a new jug of H-110 Friday to monkey with before this cold snap hit. I load a good bit of it between two .357 revolvers, a Marlin .357 carbine, and loading .410. For years my go to load for the carbine has been a Lee gas checked 158 SWC @ .359 and 15.6 grains of H-110 in Starline cases with a heavy roll crimp in the crimp groove. Loaded and shot thousands of these. They run around 1730 fps in my carbine with consistent MOA accuracy. At 63 my eyes are not what they used to be. I need readers to look at my manuals and measurements now. I started putting a 2-7 Leupold on the lever guns when I am working up or testing a load in that carbine. Any how back to opening the new jug of powder. By H-110 standards 15.6 grains is not what I consider hot but around 1730 is historically where it shoots best in my carbine. Opening a new can and all, I set up my chronograph dropped down to 15.3 grains with my normal procedure of working back up to 15.6. Checking velocity as I go. First shot at 15.3 did 1719 fps.
Hmm. Went inside and put the scope on the Marlin and loaded a few more at 15.3 and shot a 100 yard group to confirm what I was seeing. Basically the new can of powder duplicates my old 15.6 grain load with 15.3 grains.
Lot to lot variation within the same powder is worth checking for when opening a new jug of powder.
Willie