I have been shooting two different H&R single shots that are chambered for what is called the .22 PREDATOR and the .22 SUPER PREDATOR! Both of these guns will shoot under 1/2" at 100 yards when shot from a bench. The .22 PREDATOR is a rechambered 223 heavy barrel. It is kinda like a rimmed version of the 223 Ackley Improved and used 5.6X50R brass and 223 Ackley Improved dies to reload for it...

The .22 SUPER PREDATOR is a rechambered 22-250. It is basically a long necked and rimmed 22-250 Ackley Improved and uses the full length 307 Winchester case necked down. I can easily exceed the 220 Swift in velocity and shoot 1" 3-shot groups at 300 yards with this one. This barrel also has a muzzle break that allows me to watch the bullet impact it's target at anything over 100 yards...

Given your choice of rounds, the 22 hornet would be a good choice and having a 22 K-Hornet would make it even a little bit better....

DAVID