Ludicrous rule - if it's a problem, then it's been a problem for a few decades, but now that 95% of athletes are using (compliant) metal stocks, it's bad enough to need attention to rid the remaining 5%

I don't see widespread implementation. The British 50Metre Championships and the British Airgun Championships certainly will. They're key selection shoots, and they're the most prestigious UK event for those disciplines, so they need to be there or thereabouts given they are used for GB Selection and it's no good getting selected for GB using a rifle that you won't be allowed to use at an international.

The ESSU might choose to be picky about it. We don't know yet.

Certainly the NSRA's August National Meeting does not worry about such things, nor will the BFRC. I doubt the Welsh or Scottish 50M or Airgun matches will worry about it either. Overall, not really a big issue for 99.9% of shooters, but the ISSF is hardly maing life easy for organisers or selectors who either have to choose to ignore certain rules, or be "Mr Unpopular" and take the hit on their entry numbers by being strict and excluding pretty much anyone with a wooden stock.