I recall that Remington used to sell "Accelerator" ammo, which was a nearly-4000 fps .30-06 round with a .22 bullet in sabot, and I read somewhere that the reason it was discontinued was that it did not come near to the "varmint accuracy" that people expected of it. In essence, there was no advantage to a high velocity .22 bullet in a round that did not perform nearly as well as their match grade 168 grain round.