07-27-2021, 06:41 PM
I'd wager that a hot load is at least part of the problem. Hornady Black likely uses Lever near max charge, so if you put a max charge that flattens primers in a different unfireformed case without any load work up which may (or may not) have lower capacity, something is going to give somewhere. I've had more than one barrel that can't handle max published charges and that would probably go boom if I dropped a max charge of ball powder in them on a hot day.
Two thoughts: are you using an expander ball and if not, are you checking for the dreaded "donut" (ring that can form in the inside of the neck). The donut can lead to pressure spikes. It might also be worthwhile to compare the bearing surfaces of the Hornady 105 HPBT with your Berger's. If the Berger has more, you could be getting an early pressure spike, especially with the short jump. But regardless, I'd back off on the charge. The Hornady Black is telling you that.
Two thoughts: are you using an expander ball and if not, are you checking for the dreaded "donut" (ring that can form in the inside of the neck). The donut can lead to pressure spikes. It might also be worthwhile to compare the bearing surfaces of the Hornady 105 HPBT with your Berger's. If the Berger has more, you could be getting an early pressure spike, especially with the short jump. But regardless, I'd back off on the charge. The Hornady Black is telling you that.
#FJB