Mary managed to outcompete the local squirrels to the tune of 10 pounds of Shagbark Hickory nuts, which we’ve been enjoying after supper. The thickly armored nuts shrug off ordinary nutcrackers, so we deploy heavy weaponry: good old 10WR Vise-Grip pliers:
She describes the process better than I; for what it’s worth, I work on one nut at a time. We both celebrate when a shell releases its nut with minimal damage; most often, we extract fragments into a pile like the one shown. I can process half a dozen nuts before deciding I’ve had enough.
I’d be in favor of a genetic modification producing a fluorescent green shell, because overlooking a minute piece of shell in that pile of nutmeat is a Very Bad Thing…
Some Vise-Grip history may be of interest.
The Smell of Molten Projects in the Morning 
Someone made us a chocolate hickory nut pie once, very good as you might imagine. I know those shells are the next hardest thing to a diamond, but it is always nice to eat the things that are in season.
Hulling that many nuts would far exceed the half-life of the nutmeats accumulating in the pantry…
I think you would be the kind of guy that could come up with a shatter-but-don’t-crush device.
I am thinking of something that adjust to the size of the nut, then hits it with a high impact force but very little movement
The Vise-Grips do just about that, minus the impact: it’s a slow, inexorable squeeze.
I snug the Vise-Grip down on the nut (across the longest diameter, about 45° from the poles), then apply increasing force: release the grip just past the overtravel point, crank on an additional 1/16 turn, re-squeeze, iterate.
The part that always astonishes me is how much load those shells can take: the nut creaks, squeaks, and finally shatters with a loud crack after about 1/4 turn. Even though I keep two fingers on the nut, it sometimes fires fragments far across the kitchen. I can usually hold the pieces together and work it over to crack the larger hunks.
I don’t know much force the Vise-Grip applies; I’d love to measure it!
I use Vise-grip for walnuts and others local stuff. You can set the crush depth just right without smashing up the core with Vise-grip.