They make a bullet called a wadcutter. Looks like a soup can. It was designed for target shooting, and its purpose is to cut pretty round holes in the paper target (instead of tearing a hole like a round-nosed bullet does) to make scoring the target easier.
These bullets are seated flush with the case mouth, to reduce case capacity, so you can use less powder.
There are two type of wadcutters - solid, and what are called "hollow-base". They are loaded the same way, they work the same way, but the hollow-base bullet has like a skirt.
The skirt expands from the burning powder gases, to grip the barrel better, possibly giving better accuracy.
Many years ago some bright person got the idea of load HBWC bullets upside down, so that the hollow was pointed out, in effect making a HUGE hollowpoint bullet.
This was never done commercially, as far as I know, but many handloaders did this.
Now, since Hydra-shok's claim to fame is the pillar in the middle of their hollowpoints,
and those bullets have that pillar, I presume that Hydra-shok took the idea of the "upside-down HBWC", added their own special touch to it, and made those things you have.
I don't know if they STILL make 'em, but I'm sure you have factory-loaded ammo there.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.