Randy:
I was "riding recoil" today shooting those 2 ball loads! Recovery time was fairly long I'd say! Recoil wasn't an unpleasant jab, more of a big bad push that rocked me backwards... very substantial! I'm betting those 2 balls would ruin a bear's day though.
I don't think there would be any rapid succession of shooting these loads! A guy could probably get a couple or three of reasonably fast but I think the accumulated recoil would take its toll. I'm not sure as to whether the recoil using these is detrimental enough to recovery time to choose something with less recoil. I'd have to try a few in rapid succession to see if I could get more than one aimed shot off if a bear charged. Not much time to recover, work an action and aim again... bears can move fast! That is a consideration in any defensive application.
They aren't actually as heavy as your slug though! The 2 balls run about 625 grs. so hefty but not outrageous. I used 29 grs. of Blue Dot under them so based on weight and slug like bore friction I am sure that can be safely increased into the low to maybe mid 30 gr. area anyway.
That slug is still hollow base isn't it? Just smaller hollow base pin?
What powder and charge are you using under those 670 gr. slugs?
Longbow