Prepare for disappointment. You know how precision shooting is all about repeatability? Making sure optics hold zero, actions bedded and torqued to a consistent specification? Bullet weights are carefully matched to twist rates to ensure stabilization? Op-rods and springs are upgraded to make sure that bolts return to the exact same place? How barrels are free-floated and tuned to enhance the harmonics?
This is the exact opposite. A relatively short and loose liner is placed in an inconsistent spot in direct contact with a barrel, the round is fired through a 3"-8" rifled bore and the adapter flexes and bumps around in the bore as the bullet. Ready for the next round!
In terms of utility for SHTF, when was the last time you were out traipsing through the woods and came across a box of ammo? More importantly, are you willing to pack a few pounds of steel as you trek through the wilderness hoping to stumble across some 28g or 45 Long Colt to save your ass from starving, or from starving predators?
If you're looking for some fun, this may give you ####s and giggles but reviews online are not favorable.