Regardless of what anybody else believes or finds tuners do make a difference, in my case anyway.
As for effectiveness on centrefire rifles I offer no evidence or opinion.
Both my two .22lr bench rest rifles benefit from rounder groups and less vertical spread when a tuner is correctly set, note I say correctly. The impact of a tuner can be further shown by not setting it up correctly leading to an increase in vertical spread.
If tuners don’t work then the marketing gurus have had a field day, just observe the number of rifles fitted with tuners at any NSRA/WRABF benchrest competition.
I’m afraid that I must somewhat disagree with the statement that most rimfire manufacturers produce very consistent ammunition as this is not my experience. Whilst some rimfire ammunition manufacturers do produce relatively consistent ammunition they also produce less consistent ammunition. In my experience, generally, the more you pay for the ammunition the better the quality.
Consistency is difficult to quantify as we have no parameters on what consistent is and how it’s measured, so at this stage is open to interpretation.
With regards purchasing a rimfire tuner in the Uk there are, or we’re at least when I last looked, several makes available of which none needed any custom manufacture/fitting. Starik for example. Though if one has an unusual barrel profile they may not fit.
The posters tuner looks smart. One possible advantage is it’s fitting behind the muzzle, prevents the tuner getting carboned which in theory could effect its performance.
If the OP would like to send me one to evaluate I would be happy to oblige. PM via this site.
Whatever one believes if it works for you it works. Happy shooting.