Good choice...I have a .17 Hornet and love shooting it out to 300-400 yards for fun in calm conditions. But my .223 has done me A LOT better as a trainer as spotting splash is much easier alone at 400+ yards and is much more consistent in wind.
Iv been shooting the crap out of the 17 hmr lately. I think everyone needs a rimfire “trainer” as well. While mine was mainly built to kill varmints I will say now that I got a bravo on it, it’s a great gun to run drills with while my centerfire rifles cool off.
Sub 200 with the 17 is also great spotting practice, small bullet moving at near centerfire speeds. But past 200 it’s near impossible to see steel move, even the thin stuff.
Plus it’s cheap to shoot without reloading, shoot it has better accuracy now than my 223 tikka does, I’m sure that will change when it comes back from LRI.
I shoot my 17HMR’s quite a bit to almost 200 and like them for small varmint hunting, sage rats and PD’s and the like. Very accurate and no recoil. You can practice positions and trigger control, etc. But they are nearly useless in the wind at any distance. They are good practice, but I don't see them as a substitute for a .223/5.56.
Besides small varmints, what I think they excel at is helping a new shooter build confidence and competence before moving up to a .223 class cartridge. We have a rimfire silhouette range at my club with numerous small metal targets. Some are not easy to knock over with the 17HMR for my grands. So it requires them to hit a spot on the target, often the head. Real good practice for them. 50-100 rounds there then off to the 100, 200 & 300 ranges with the .223.
The kapow of a center fire is also good practice for them. That’s how I use my 17HMR’s anyway. So I say make sure you have both.