The Firing Line Forums - View Single Post - is it a must to work up new load when changing powder lots

Clark · July 22, 2014, 03:10 PM

CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

I handload over 5 dozen cartridges.
I have overloaded over 2 dozen cartridges to the point of destruction just to see what would happen.
I have overloaded the 308 and other cartridges with similar case heads; 6mmBR, 243, 257RAI, 260, 270, 30-06, and 8x57.

The 6mmBR is the exception because of the small rifle primer pocket. The weak spot in a work up is a pierced primer.

The 308 and the others will get a loose primer pocket as the limit. I measure the extractor groove growth as a more sensitive and consistent precursor to loose primers.

If I play with Quickload so that the velocity predicted matches the velocity measured, I get a consistant pressure of loose primer pockets across the Mauser case head cartridges.

Measuring that threshold and measuring those velocities allows me to compare different lots of powder.

I have found the difference between IMR4895 lot to lot and H4895 not to be a big deal, and can be down in the noise of the other variables I account for in my derating by a safety margin from the threshold of lose primer pockets.

What is different is bulk 4895 pull down surplus powder.
I have found as much as a 9% difference between that and the fancy canister 4895 powder from the gun store.

July 22, 2014, 03:10 PM	#41
Clark Senior Member Join Date: December 4, 1999 Location: WA, the ever blue state Posts: 4,678	CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information. I handload over 5 dozen cartridges. I have overloaded over 2 dozen cartridges to the point of destruction just to see what would happen. I have overloaded the 308 and other cartridges with similar case heads; 6mmBR, 243, 257RAI, 260, 270, 30-06, and 8x57. The 6mmBR is the exception because of the small rifle primer pocket. The weak spot in a work up is a pierced primer. The 308 and the others will get a loose primer pocket as the limit. I measure the extractor groove growth as a more sensitive and consistent precursor to loose primers. If I play with Quickload so that the velocity predicted matches the velocity measured, I get a consistant pressure of loose primer pockets across the Mauser case head cartridges. Measuring that threshold and measuring those velocities allows me to compare different lots of powder. I have found the difference between IMR4895 lot to lot and H4895 not to be a big deal, and can be down in the noise of the other variables I account for in my derating by a safety margin from the threshold of lose primer pockets. What is different is bulk 4895 pull down surplus powder. I have found as much as a 9% difference between that and the fancy canister 4895 powder from the gun store.