Keep the 223 . You already have a 17 hornet so you don't need a 22 hornet.
The Hornet will kill foxes very well to 150 yards you mention no trouble at all if you play your part correctly . Avoid 35 v max as they have such a bad BC the tiny extra muzzle velocity is gone in a flash . 40 + 45 grain like the seirra are way better by a large amount after you pass about 140 yards . Its real advantage though is its easier to moderate over a 223 rem and if you buy a CZ the gun itself is a lot lighter than the 223 rem but be carefull there is none of that if the only difference if its built on a 223 based rifleOnly use my .223 for foxes and generally under 150yards, thinking of parting with it to be replaced with a .22 hornet.
Thinking I would save on reloading costs as use less powder, have brass as also have a .17hornet and i neck down .22 to .17.
good idea or not?
Advantages vs disadvantages?
The Hornet will kill foxes very well to 150 yards you mention no trouble at all if you play your part correctly . Avoid 35 v max as they have such a bad BC the tiny extra muzzle velocity is gone in a flash . 40 + 45 grain like the seirra are way better by a large amount after you pass about 140 yards . Its real advantage though is its easier to moderate over a 223 rem and if you buy a CZ the gun itself is a lot lighter than the 223 rem but be carefull there is none of that if the only difference if its built on a 223 based rifle
I also have a 223 which can fire longer range and help stiffer winds with a 50-60 grain bullet and about twice the powder and more heft to carry and that gets worse if your 223 is built in the likes of a tikka that don't get calibre specific ( might as well get a 243 or 22-250 than do that IMHO.
Now "copper " forget the .22 hornet with very slow twist rates - it aint going to be pretty but don't fret because the CZ and other hornet specific rifles are never going to fit in your mag and the extractors wont work etc etc .
Half the powder of a 223 remember , no real chance of copper in the CZ and slow-slow twists . Redeemed by using it on rabbits near and far , if you have the skill 300 yard head shots on rabbits is very doable in skilled hands.
If you don't get a 22 hornet now you likely never will if the copper bullet becomes the only choice
"More efficient" than a 22 Hornet?I could be wrong, but I suspect the .22 Hornet is what could be described as a "nostalgic" calibre. Many, like me, have memories of the good old Hornet from the days when there were few calibres available. I always loved the Hornet, but admit that these days there are more efficient calibres available. I recently sold my own Anschutz Hornet as it was not getting used very much. Do I miss it? Yes, would I get another, probably not.

I've used hornet before. 22 not a 17. And for fox I would without thinking about it, keep the 223. I've got two 223 sako rifles. Excellent.Only use my .223 for foxes and generally under 150yards, thinking of parting with it to be replaced with a .22 hornet.
Thinking I would save on reloading costs as use less powder, have brass as also have a .17hornet and i neck down .22 to .17.
good idea or not?
Advantages vs disadvantages?
Go for it then and scratch the itch. 40 grain Sierra SP over a case full of Lil'gun should get you going nicely.I reload and have that same itchall I would need is a set of dies.