Big Pressure Change

[Jerry]

Have shot 41 grs. H4350 in my 6 x 47L for two 1K seasons using 106 Clinch River Bullets, jammed .015 with no problems.
Got three cans of H4350 for Christmas and blended them for uniformity. Have always blended in new with old powder to average the speed. First time shooting the new powder was at the first match. Hard bolt lift, ejecter marks and two primers that fell out. Checked absolutely everything and the new powder is the only difference. Pulled bullets and weighed unshot rounds. Dead on.
Soooo. Must be a faster lot of powder. Since it was a hot load before, the new faster powder must have pushed me over the edge!
Any thoughts on this? Happened to any of you?
Jerry

 

[Bill Edwards]

Yup! If you work up a max. ld at a cooler temp like 32 degrees and shoot that same ld. at 70 degrees it'll do just what you describe nearly every time. Some powder is worse than others about that too. Altitude makes a difference too. Gotta be careful w/ those max. loads.

 

[Mark S in NM]

You blended powder . See "Slow batch of Varget" a few posts down.

 

[cmillard]

when was the last time you fl sized your cases. i know that if i go more than 5 firings without fl sizing and only neck sizing, that 6th firing will usually show excess pressure in my 6BR. otherwise, all previous firings show normal pressure

 

[RDavies]

You are shooting a max load for this combo, with not much safety factor. When switching to a new lot of powder, I always crony a few shots with my new and old lot so I know what charge it needs to keep in tune.