Ive got one, a cooper stainless, 20" with 1-10 twist,
Ive got it back in New Zealand now, and use it as a dual purpose rifle, for small game, goats,wallabys and fallow deer, mostly shot the 75gr serria HP, or 85gr serria, must try a few partions, have shot three deer, a pig and a dozen goats now, works very good for what I am doing.
Handy we cartridge, But with the .223 fast twist and more choices, in .22 heavy bullets, doesn't offer much more than the fast twist .223 can.
5gr heavier bullet, a touch faster (50-100 fps) than the .223, is how I look at it.
More 6mm bullets, suitable for hunting, but depending on your action length, you may not be able to use them.