My assertion is a tuner cant fix a bad rifle setup or poor ammunition in regards to Rimfire accuracy. Their are more variables that effect performance that should be looked into before relying on a tuner. Centerfire, tuner results are way more effective. So im not saying they dont work, they just dont work enough to see effective change if your rocking a 1.20" or larger straight barrel in Rimfire.
headspace directly effects ignition as well as how your firing pin strikes. Its a big factor in all 22lr rifles in general and often over looked to replace firing pin springs. Match grade barrels or production, you can see the difference when changing these variables.
As I've seen during lot testing, change in firing pin springs or headspace drastically changed rifles performance and preference in the ammunition lot. You can get creative by adding spacers between firing pin springs, or order new ones from various spring manufacturers. Many CZ457 owners also play with bolt shims for headspace.
I've seen your input in the community and gladly have data to share proof both systems, tuner on thinner barrels or these variables both affect group size, with headspace and spring rate changes more effectively "tune" a rifle to perform better over various lots or ammo type
