Via email from Toastrider we have this:
For some reason I haven’t been able to find any commercially available ammo. It must be that a high demand for it hoovered the shelves like a lot of the other ammo. This would appear to be consistent with the abundance of large rifle ammo, moderate availability of .223 ammo, and scarcity of .22 ammo. Thus I claim we have proof that if the size of a gun is inversely related to penis size then the caliber of the gun owning man in this country is much larger than average.