The barrel is best left as it is. A model 70 action is way overkill for the little Hornet, but they are neat guns, and the K-Hornet does get it done a little faster. Light bullets are what it will use, 40 - 45 grain jobs.
If you want a 223 have it rebarreled with a faster twist. I had one years ago, a 22 Hornet model 70 action opened up to 223. It had a Remington 722 magazine box and follower grafted into a model 70 magazine box and it fed as a repeater. Many 22 Hornet to 222 / 223 are single shots. I don't remember whether they used a Hornet mag box or 30-06 or what. I didn't do the work or had someone else do the work. I bought it from the builder.
