Thorny,
There is also a Marlin cheapie autoloader 22, that has some 'sort of "Microgroove" barrel on it. I haven't honestly shot it at 50 yards (mostly, kids in gunsafety class used it to poke their first holes in paper targets). But, I have been startled on two occasions of informal group plinking on how accurate a little gun it is.
That Remington 581, with the shortened and squared at both ends barrel, target crown, cleaned up trigger group, and Shepard scope? Now there, my friend, we would have a race....
Best,
Ted