Despite the name this cartridge was invented by P.O. Ackley a prolific American wildcatter. Wildcat cartridges are ones that are not made to a standard adopted by any major manufacturer.
This particular cartridge could send a .22 caliber round 5,000 fps (1,524 m/s). The case it uses in this picture is that of a .378 Weatherby Magnum necked down to hold a .223 caliber bullet, but another design of the same name used .50 BMG cases.
Shooting .22 out of .378 barrel doesn’t seem like the path to accuracy.
Thats not what’s happening though. The Casing is a .378 case but the neck of the case (which holds the bullet in place) is formed down to .223. The barrel is also presumed to be .223 diameter with a chamber that is reamed out to accommodate the length and diameter of the cartridge to be fired. It’s a path to putting a ton of powder behind a small diameter bullet (much like an even more extreme version some more modern calibers like 6.5-300 weatherby magnum). Actually with a little work (and some very long and heavy .223 diameter bullets) you could probably make this thing hilariously accurate for a thousand rounds or so before you absolutely wrecked the rifling.
I agree. Every round would be hand loaded (because no company loads it). And precision is nothing more than repeatability. If you’ve found a good action and barrel nothing should stop you from shooting sub MOA groups.
For the most part particular chamberings are only more or less ‘accurate’ based on the ballistic coefficient / drop and the standard at which the manufacturer makes the cartridges.