Back in the '60's in my area a wildcat cartridge called the 6mm/.284 became all the rage. Fantastic velocities were reported with fantastic accuracy. The only problem was that by the time the rifle was well sighted in, the throat was burned out.

Years later, shooting the .243 Winchester in high power competition became all the rage, once suitable high ballistic coefficient bullets for long range had been developed, but the phenomenon of some bullets exploding in mid air from having the jackets succomb to centrifical force at the required quick twist rates, and excessive throat wear, allowing for perhaps 1000 shots before the barrel had to be set back and rechambered or replaced, killed it off. Today the top shooters are using a 6mm based on the .22-.250 case and 1000 yard competitors are using 6mm PPC's, which are even smaller. Barrel life is in the same range as the .308, about 2000 rounds.

The 5.6X57 was wildcatted in this country back in the '50's, in the form of the .22-.257 or .220 Clark, but never caught on. The .22-.250 or the .220 Swift will do anything it could do, but with less powder. The 57mm case badly exceeds the point of diminishing returns for a .22 caliber bore.

If I were to experiment with a heavy bullet .22, I would start with the PPC case and work up. As far as heavy bullet .22's are concerned, the .22 Savage High Power is a deadly killer in open spaces, where brush or other obstructions are not a concern. Its case capacity is 36.70 grains of water, versus 32.65 for the .22 PPC and 46.79 grains for the 5.6X57.